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	$223.38	11.208%	$248.4164	$248.42	$248.40	$248.40
Purchase #2	$25.63	12.846%	$28.9224	$28.92	$28.90	$28.90
Purchase #3	$30.86	12.660%	$34.7669	$34.77	$34.75	$34.80
Purchase #4	$53.69	7.525%	$57.7302	$57.73	$57.75	$57.70
Purchase #5	$111.44	10.814%	$123.4911	$123.49	$123.50	$123.50
Purchase #6	$216.98	4.696%	$227.1694	$227.17	$227.15	$227.20
Purchase #7	$191.25	10.350%	$211.0444	$211.04	$211.05	$211.00
7 purchase totals =	$853.23		$931.5408	$931.54	$931.50	$931.50