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	$176.73	12.327%	$198.5155	$198.52	$198.50	$198.50
Purchase #2	$41.57	4.360%	$43.3825	$43.38	$43.40	$43.40
Purchase #3	$220.66	5.863%	$233.5973	$233.60	$233.60	$233.60
Purchase #4	$97.45	3.874%	$101.2252	$101.23	$101.25	$101.20
Purchase #5	$190.83	4.855%	$200.0948	$200.09	$200.10	$200.10
Purchase #6	$207.30	7.494%	$222.8351	$222.84	$222.85	$222.80
Purchase #7	$216.85	6.834%	$231.6695	$231.67	$231.65	$231.70
7 purchase totals =	$1,151.39		$1,231.3199	$1,231.33	$1,231.35	$1,231.30