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	$65.65	8.869%	$71.4725	$71.47	$71.45	$71.50
Purchase #2	$242.79	9.737%	$266.4305	$266.43	$266.45	$266.40
Purchase #3	$133.57	9.248%	$145.9226	$145.92	$145.90	$145.90
Purchase #4	$59.27	3.411%	$61.2917	$61.29	$61.30	$61.30
Purchase #5	$177.41	6.764%	$189.41	$189.41	$189.40	$189.40
Purchase #6	$83.54	8.182%	$90.3752	$90.38	$90.40	$90.40
Purchase #7	$124.55	3.117%	$128.4322	$128.43	$128.45	$128.40
7 purchase totals =	$886.78		$953.3347	$953.33	$953.35	$953.30