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	$220.62	9.851%	$242.3533	$242.35	$242.35	$242.40
Purchase #2	$134.34	5.439%	$141.6468	$141.65	$141.65	$141.60
Purchase #3	$219.53	9.675%	$240.7695	$240.77	$240.75	$240.80
Purchase #4	$169.91	11.309%	$189.1251	$189.13	$189.15	$189.10
Purchase #5	$157.52	5.687%	$166.4782	$166.48	$166.50	$166.50
Purchase #6	$186.32	5.386%	$196.3552	$196.36	$196.35	$196.40
Purchase #7	$38.49	4.854%	$40.3583	$40.36	$40.35	$40.40
7 purchase totals =	$1,126.73		$1,217.0864	$1,217.10	$1,217.10	$1,217.20