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	$151.76	13.376%	$172.0594	$172.06	$172.05	$172.10
Purchase #2	$58.95	3.811%	$61.1966	$61.20	$61.20	$61.20
Purchase #3	$197.38	13.683%	$224.3875	$224.39	$224.40	$224.40
Purchase #4	$167.69	6.420%	$178.4557	$178.46	$178.45	$178.50
Purchase #5	$249.40	11.228%	$277.4026	$277.40	$277.40	$277.40
Purchase #6	$93.85	6.527%	$99.9756	$99.98	$100.00	$100.00
Purchase #7	$226.44	6.380%	$240.8869	$240.89	$240.90	$240.90
7 purchase totals =	$1,145.47		$1,254.3643	$1,254.38	$1,254.40	$1,254.50