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	$176.87	8.399%	$191.7253	$191.73	$191.75	$191.70
Purchase #2	$123.38	13.596%	$140.1547	$140.15	$140.15	$140.20
Purchase #3	$152.54	8.768%	$165.9147	$165.91	$165.90	$165.90
Purchase #4	$228.31	9.856%	$250.8122	$250.81	$250.80	$250.80
Purchase #5	$58.60	7.550%	$63.0243	$63.02	$63.00	$63.00
Purchase #6	$35.58	5.403%	$37.5024	$37.50	$37.50	$37.50
Purchase #7	$100.95	13.323%	$114.3996	$114.40	$114.40	$114.40
7 purchase totals =	$876.23		$963.5332	$963.52	$963.50	$963.50