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	$103.52	11.601%	$115.5294	$115.53	$115.55	$115.50
Purchase #2	$72.98	12.580%	$82.1609	$82.16	$82.15	$82.20
Purchase #3	$26.62	13.869%	$30.3119	$30.31	$30.30	$30.30
Purchase #4	$118.71	7.120%	$127.1622	$127.16	$127.15	$127.20
Purchase #5	$230.61	3.779%	$239.3248	$239.32	$239.30	$239.30
Purchase #6	$45.63	10.397%	$50.3742	$50.37	$50.35	$50.40
Purchase #7	$79.54	3.551%	$82.3645	$82.36	$82.35	$82.40
7 purchase totals =	$677.61		$727.2279	$727.21	$727.15	$727.30