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	$91.74	8.272%	$99.3287	$99.33	$99.35	$99.30
Purchase #2	$150.82	12.289%	$169.3543	$169.35	$169.35	$169.40
Purchase #3	$187.27	6.201%	$198.8826	$198.88	$198.90	$198.90
Purchase #4	$144.84	10.819%	$160.5102	$160.51	$160.50	$160.50
Purchase #5	$132.89	8.251%	$143.8548	$143.85	$143.85	$143.90
Purchase #6	$245.53	10.180%	$270.525	$270.53	$270.55	$270.50
Purchase #7	$80.32	5.483%	$84.7239	$84.72	$84.70	$84.70
7 purchase totals =	$1,033.41		$1,127.1795	$1,127.17	$1,127.20	$1,127.20