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	$172.66	11.142%	$191.8978	$191.90	$191.90	$191.90
Purchase #2	$183.88	13.506%	$208.7148	$208.71	$208.70	$208.70
Purchase #3	$228.84	11.237%	$254.5548	$254.55	$254.55	$254.60
Purchase #4	$96.57	9.167%	$105.4226	$105.42	$105.40	$105.40
Purchase #5	$236.70	9.476%	$259.1297	$259.13	$259.15	$259.10
Purchase #6	$118.63	6.520%	$126.3647	$126.36	$126.35	$126.40
Purchase #7	$16.54	11.809%	$18.4932	$18.49	$18.50	$18.50
7 purchase totals =	$1,053.82		$1,164.5776	$1,164.56	$1,164.55	$1,164.60