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	$140.96	10.248%	$155.4056	$155.41	$155.40	$155.40
Purchase #2	$181.98	12.265%	$204.2998	$204.30	$204.30	$204.30
Purchase #3	$49.73	10.293%	$54.8487	$54.85	$54.85	$54.80
Purchase #4	$33.74	12.191%	$37.8532	$37.85	$37.85	$37.90
Purchase #5	$196.25	13.408%	$222.5632	$222.56	$222.55	$222.60
Purchase #6	$154.45	11.743%	$172.5871	$172.59	$172.60	$172.60
Purchase #7	$89.45	11.364%	$99.6151	$99.62	$99.60	$99.60
7 purchase totals =	$846.56		$947.1727	$947.18	$947.15	$947.20