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	$143.63	13.386%	$162.8563	$162.86	$162.85	$162.90
Purchase #2	$151.69	10.157%	$167.0972	$167.10	$167.10	$167.10
Purchase #3	$129.68	5.873%	$137.2961	$137.30	$137.30	$137.30
Purchase #4	$191.57	10.518%	$211.7193	$211.72	$211.70	$211.70
Purchase #5	$235.28	4.183%	$245.1218	$245.12	$245.10	$245.10
Purchase #6	$72.75	13.606%	$82.6484	$82.65	$82.65	$82.60
Purchase #7	$176.74	7.654%	$190.2677	$190.27	$190.25	$190.30
7 purchase totals =	$1,101.34		$1,197.0068	$1,197.02	$1,196.95	$1,197.00