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	$64.69	3.583%	$67.0078	$67.01	$67.00	$67.00
Purchase #2	$60.38	11.167%	$67.1226	$67.12	$67.10	$67.10
Purchase #3	$37.83	6.463%	$40.275	$40.28	$40.30	$40.30
Purchase #4	$17.73	10.697%	$19.6266	$19.63	$19.65	$19.60
Purchase #5	$65.68	10.346%	$72.4753	$72.48	$72.50	$72.50
Purchase #6	$90.64	12.603%	$102.0634	$102.06	$102.05	$102.10
Purchase #7	$155.35	4.242%	$161.9399	$161.94	$161.95	$161.90
7 purchase totals =	$492.30		$530.5106	$530.52	$530.55	$530.50