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	$211.59	12.740%	$238.5466	$238.55	$238.55	$238.50
Purchase #2	$40.52	5.606%	$42.7916	$42.79	$42.80	$42.80
Purchase #3	$88.31	12.182%	$99.0679	$99.07	$99.05	$99.10
Purchase #4	$99.87	6.579%	$106.4404	$106.44	$106.45	$106.40
Purchase #5	$235.56	3.477%	$243.7504	$243.75	$243.75	$243.80
Purchase #6	$144.64	8.366%	$156.7406	$156.74	$156.75	$156.70
Purchase #7	$244.93	4.364%	$255.6187	$255.62	$255.60	$255.60
7 purchase totals =	$1,065.42		$1,142.9562	$1,142.96	$1,142.95	$1,142.90