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	$36.32	13.192%	$41.1113	$41.11	$41.10	$41.10
Purchase #2	$235.70	4.237%	$245.6866	$245.69	$245.70	$245.70
Purchase #3	$211.32	5.413%	$222.7588	$222.76	$222.75	$222.80
Purchase #4	$244.48	6.852%	$261.2318	$261.23	$261.25	$261.20
Purchase #5	$137.85	9.813%	$151.3772	$151.38	$151.40	$151.40
Purchase #6	$111.51	8.167%	$120.617	$120.62	$120.60	$120.60
Purchase #7	$93.94	9.828%	$103.1724	$103.17	$103.15	$103.20
7 purchase totals =	$1,071.12		$1,145.9551	$1,145.96	$1,145.95	$1,146.00