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	$169.66	11.145%	$188.5686	$188.57	$188.55	$188.60
Purchase #2	$202.77	4.307%	$211.5033	$211.50	$211.50	$211.50
Purchase #3	$242.87	10.290%	$267.8613	$267.86	$267.85	$267.90
Purchase #4	$111.72	7.818%	$120.4543	$120.45	$120.45	$120.50
Purchase #5	$29.92	6.283%	$31.7999	$31.80	$31.80	$31.80
Purchase #6	$125.55	9.464%	$137.4321	$137.43	$137.45	$137.40
Purchase #7	$125.82	11.102%	$139.7885	$139.79	$139.80	$139.80
7 purchase totals =	$1,008.31		$1,097.4080	$1,097.40	$1,097.40	$1,097.50