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	$78.48	13.658%	$89.1988	$89.20	$89.20	$89.20
Purchase #2	$46.29	3.457%	$47.8902	$47.89	$47.90	$47.90
Purchase #3	$53.95	8.704%	$58.6458	$58.65	$58.65	$58.60
Purchase #4	$70.44	12.787%	$79.4472	$79.45	$79.45	$79.40
Purchase #5	$37.38	3.742%	$38.7788	$38.78	$38.80	$38.80
Purchase #6	$57.96	7.233%	$62.1522	$62.15	$62.15	$62.20
Purchase #7	$76.96	11.453%	$85.7742	$85.77	$85.75	$85.80
7 purchase totals =	$421.46		$461.8872	$461.89	$461.90	$461.90