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	$59.61	9.537%	$65.295	$65.30	$65.30	$65.30
Purchase #2	$156.98	9.271%	$171.5336	$171.53	$171.55	$171.50
Purchase #3	$171.58	9.705%	$188.2318	$188.23	$188.25	$188.20
Purchase #4	$67.84	5.230%	$71.388	$71.39	$71.40	$71.40
Purchase #5	$225.91	4.258%	$235.5292	$235.53	$235.55	$235.50
Purchase #6	$61.58	8.231%	$66.6486	$66.65	$66.65	$66.60
Purchase #7	$152.28	6.849%	$162.7097	$162.71	$162.70	$162.70
7 purchase totals =	$895.78		$961.3359	$961.34	$961.40	$961.20