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	$103.26	9.788%	$113.3671	$113.37	$113.35	$113.40
Purchase #2	$74.44	10.657%	$82.3731	$82.37	$82.35	$82.40
Purchase #3	$141.62	12.581%	$159.4372	$159.44	$159.45	$159.40
Purchase #4	$67.72	3.593%	$70.1532	$70.15	$70.15	$70.20
Purchase #5	$237.47	8.165%	$256.8594	$256.86	$256.85	$256.90
Purchase #6	$72.42	12.498%	$81.4711	$81.47	$81.45	$81.50
Purchase #7	$159.90	13.264%	$181.1091	$181.11	$181.10	$181.10
7 purchase totals =	$856.83		$944.7702	$944.77	$944.70	$944.90