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	$182.96	11.372%	$203.7662	$203.77	$203.75	$203.80
Purchase #2	$29.39	11.714%	$32.8327	$32.83	$32.85	$32.80
Purchase #3	$105.74	6.819%	$112.9504	$112.95	$112.95	$113.00
Purchase #4	$83.43	7.763%	$89.9067	$89.91	$89.90	$89.90
Purchase #5	$229.37	6.285%	$243.7859	$243.79	$243.80	$243.80
Purchase #6	$154.38	12.589%	$173.8149	$173.81	$173.80	$173.80
Purchase #7	$233.86	9.636%	$256.3947	$256.39	$256.40	$256.40
7 purchase totals =	$1,019.13		$1,113.4515	$1,113.45	$1,113.45	$1,113.50