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	$165.38	9.514%	$181.1143	$181.11	$181.10	$181.10
Purchase #2	$137.64	10.108%	$151.5527	$151.55	$151.55	$151.60
Purchase #3	$26.54	5.317%	$27.9511	$27.95	$27.95	$28.00
Purchase #4	$18.82	11.271%	$20.9412	$20.94	$20.95	$20.90
Purchase #5	$132.78	6.464%	$141.3629	$141.36	$141.35	$141.40
Purchase #6	$65.62	7.384%	$70.4654	$70.47	$70.45	$70.50
Purchase #7	$110.39	7.693%	$118.8823	$118.88	$118.90	$118.90
7 purchase totals =	$657.17		$712.2699	$712.26	$712.25	$712.40