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	$158.61	6.192%	$168.4311	$168.43	$168.45	$168.40
Purchase #2	$188.33	4.323%	$196.4715	$196.47	$196.45	$196.50
Purchase #3	$109.90	11.293%	$122.311	$122.31	$122.30	$122.30
Purchase #4	$13.65	3.337%	$14.1055	$14.11	$14.10	$14.10
Purchase #5	$91.70	4.426%	$95.7586	$95.76	$95.75	$95.80
Purchase #6	$76.29	11.610%	$85.1473	$85.15	$85.15	$85.10
Purchase #7	$170.60	10.716%	$188.8815	$188.88	$188.90	$188.90
7 purchase totals =	$809.08		$871.1065	$871.11	$871.10	$871.10