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	$132.81	7.125%	$142.2727	$142.27	$142.25	$142.30
Purchase #2	$195.83	8.164%	$211.8176	$211.82	$211.80	$211.80
Purchase #3	$139.62	8.113%	$150.9474	$150.95	$150.95	$150.90
Purchase #4	$57.59	3.408%	$59.5527	$59.55	$59.55	$59.60
Purchase #5	$223.51	6.612%	$238.2885	$238.29	$238.30	$238.30
Purchase #6	$204.95	4.274%	$213.7096	$213.71	$213.70	$213.70
Purchase #7	$14.52	6.106%	$15.4066	$15.41	$15.40	$15.40
7 purchase totals =	$968.83		$1,031.9951	$1,032.00	$1,031.95	$1,032.00