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	$128.69	13.722%	$146.3488	$146.35	$146.35	$146.30
Purchase #2	$147.67	5.570%	$155.8952	$155.90	$155.90	$155.90
Purchase #3	$115.53	13.376%	$130.9833	$130.98	$131.00	$131.00
Purchase #4	$215.28	5.854%	$227.8825	$227.88	$227.90	$227.90
Purchase #5	$120.81	3.823%	$125.4286	$125.43	$125.45	$125.40
Purchase #6	$138.34	3.852%	$143.6689	$143.67	$143.65	$143.70
Purchase #7	$111.95	7.500%	$120.3463	$120.35	$120.35	$120.30
7 purchase totals =	$978.27		$1,050.5536	$1,050.56	$1,050.60	$1,050.50