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	$226.38	10.836%	$250.9105	$250.91	$250.90	$250.90
Purchase #2	$152.89	12.790%	$172.4446	$172.44	$172.45	$172.40
Purchase #3	$86.43	5.659%	$91.3211	$91.32	$91.30	$91.30
Purchase #4	$108.96	12.679%	$122.775	$122.78	$122.80	$122.80
Purchase #5	$150.68	9.581%	$165.1167	$165.12	$165.10	$165.10
Purchase #6	$250.41	4.863%	$262.5874	$262.59	$262.60	$262.60
Purchase #7	$27.67	12.416%	$31.1055	$31.11	$31.10	$31.10
7 purchase totals =	$1,003.42		$1,096.2608	$1,096.27	$1,096.25	$1,096.20