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	$149.29	4.699%	$156.3051	$156.31	$156.30	$156.30
Purchase #2	$144.93	4.594%	$151.5881	$151.59	$151.60	$151.60
Purchase #3	$115.80	6.120%	$122.887	$122.89	$122.90	$122.90
Purchase #4	$5.85	7.449%	$6.2858	$6.29	$6.30	$6.30
Purchase #5	$196.51	11.585%	$219.2757	$219.28	$219.30	$219.30
Purchase #6	$162.36	10.282%	$179.0539	$179.05	$179.05	$179.10
Purchase #7	$64.29	10.464%	$71.0173	$71.02	$71.00	$71.00
7 purchase totals =	$839.03		$906.4129	$906.43	$906.45	$906.50