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	$209.42	12.207%	$234.9839	$234.98	$235.00	$235.00
Purchase #2	$180.72	4.537%	$188.9193	$188.92	$188.90	$188.90
Purchase #3	$56.49	5.719%	$59.7207	$59.72	$59.70	$59.70
Purchase #4	$232.48	7.658%	$250.2833	$250.28	$250.30	$250.30
Purchase #5	$165.50	3.732%	$171.6765	$171.68	$171.70	$171.70
Purchase #6	$203.57	8.656%	$221.191	$221.19	$221.20	$221.20
Purchase #7	$111.78	10.769%	$123.8176	$123.82	$123.80	$123.80
7 purchase totals =	$1,159.96		$1,250.5923	$1,250.59	$1,250.60	$1,250.60