Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$143.64	10.254%	$158.3688	$158.37	$158.35	$158.40
Purchase #2	$95.73	7.530%	$102.9385	$102.94	$102.95	$102.90
Purchase #3	$248.74	12.771%	$280.5066	$280.51	$280.50	$280.50
Purchase #4	$214.76	13.366%	$243.4648	$243.46	$243.45	$243.50
Purchase #5	$211.94	10.582%	$234.3675	$234.37	$234.35	$234.40
Purchase #6	$188.61	6.205%	$200.3133	$200.31	$200.30	$200.30
Purchase #7	$183.51	7.279%	$196.8677	$196.87	$196.85	$196.90
7 purchase totals =	$1,286.93		$1,416.8272	$1,416.83	$1,416.75	$1,416.90