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	$89.29	7.787%	$96.243	$96.24	$96.25	$96.20
Purchase #2	$170.50	4.420%	$178.0361	$178.04	$178.05	$178.00
Purchase #3	$135.46	7.126%	$145.1129	$145.11	$145.10	$145.10
Purchase #4	$111.33	12.221%	$124.9356	$124.94	$124.95	$124.90
Purchase #5	$103.38	7.840%	$111.485	$111.49	$111.50	$111.50
Purchase #6	$111.80	10.654%	$123.7112	$123.71	$123.70	$123.70
Purchase #7	$144.43	5.178%	$151.9086	$151.91	$151.90	$151.90
7 purchase totals =	$866.19		$931.4324	$931.44	$931.45	$931.30