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	$172.51	7.780%	$185.9313	$185.93	$185.95	$185.90
Purchase #2	$98.94	12.398%	$111.2066	$111.21	$111.20	$111.20
Purchase #3	$244.48	12.640%	$275.3823	$275.38	$275.40	$275.40
Purchase #4	$211.40	8.108%	$228.5403	$228.54	$228.55	$228.50
Purchase #5	$149.81	8.529%	$162.5873	$162.59	$162.60	$162.60
Purchase #6	$186.79	5.379%	$196.8374	$196.84	$196.85	$196.80
Purchase #7	$241.34	11.163%	$268.2808	$268.28	$268.30	$268.30
7 purchase totals =	$1,305.27		$1,428.7660	$1,428.77	$1,428.85	$1,428.70