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	$59.65	3.557%	$61.7718	$61.77	$61.75	$61.80
Purchase #2	$94.48	12.867%	$106.6367	$106.64	$106.65	$106.60
Purchase #3	$51.25	12.712%	$57.7649	$57.76	$57.75	$57.80
Purchase #4	$90.69	8.566%	$98.4585	$98.46	$98.45	$98.50
Purchase #5	$137.58	6.452%	$146.4567	$146.46	$146.45	$146.50
Purchase #6	$141.97	12.409%	$159.5871	$159.59	$159.60	$159.60
Purchase #7	$63.99	11.654%	$71.4474	$71.45	$71.45	$71.40
7 purchase totals =	$639.61		$702.1231	$702.13	$702.10	$702.20