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	$41.66	10.276%	$45.941	$45.94	$45.95	$45.90
Purchase #2	$93.65	6.203%	$99.4591	$99.46	$99.45	$99.50
Purchase #3	$29.66	13.162%	$33.5638	$33.56	$33.55	$33.60
Purchase #4	$111.72	6.408%	$118.879	$118.88	$118.90	$118.90
Purchase #5	$69.77	4.453%	$72.8769	$72.88	$72.90	$72.90
Purchase #6	$115.44	3.148%	$119.0741	$119.07	$119.05	$119.10
Purchase #7	$153.39	3.109%	$158.1589	$158.16	$158.15	$158.20
7 purchase totals =	$615.29		$647.9528	$647.95	$647.95	$648.10