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	$72.85	12.823%	$82.1916	$82.19	$82.20	$82.20
Purchase #2	$89.73	11.648%	$100.1818	$100.18	$100.20	$100.20
Purchase #3	$209.76	12.479%	$235.936	$235.94	$235.95	$235.90
Purchase #4	$232.64	11.745%	$259.9636	$259.96	$259.95	$260.00
Purchase #5	$56.90	11.583%	$63.4907	$63.49	$63.50	$63.50
Purchase #6	$206.46	7.385%	$221.7071	$221.71	$221.70	$221.70
Purchase #7	$214.55	8.442%	$232.6623	$232.66	$232.65	$232.70
7 purchase totals =	$1,082.89		$1,196.1331	$1,196.13	$1,196.15	$1,196.20