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	$246.75	3.396%	$255.1296	$255.13	$255.15	$255.10
Purchase #2	$90.81	11.231%	$101.0089	$101.01	$101.00	$101.00
Purchase #3	$165.34	11.545%	$184.4285	$184.43	$184.45	$184.40
Purchase #4	$235.91	7.565%	$253.7566	$253.76	$253.75	$253.80
Purchase #5	$91.43	3.191%	$94.3475	$94.35	$94.35	$94.30
Purchase #6	$167.41	9.818%	$183.8463	$183.85	$183.85	$183.80
Purchase #7	$141.33	8.196%	$152.9134	$152.91	$152.90	$152.90
7 purchase totals =	$1,138.98		$1,225.4308	$1,225.44	$1,225.45	$1,225.30