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	$83.51	13.130%	$94.4749	$94.47	$94.45	$94.50
Purchase #2	$47.73	10.330%	$52.6605	$52.66	$52.65	$52.70
Purchase #3	$99.41	11.252%	$110.5956	$110.60	$110.60	$110.60
Purchase #4	$62.63	3.646%	$64.9135	$64.91	$64.90	$64.90
Purchase #5	$172.38	13.705%	$196.0047	$196.00	$196.00	$196.00
Purchase #6	$7.48	3.148%	$7.7155	$7.72	$7.70	$7.70
Purchase #7	$56.31	8.781%	$61.2546	$61.25	$61.25	$61.30
7 purchase totals =	$529.45		$587.6193	$587.61	$587.55	$587.70