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	$246.60	5.146%	$259.29	$259.29	$259.30	$259.30
Purchase #2	$171.55	12.264%	$192.5889	$192.59	$192.60	$192.60
Purchase #3	$119.84	8.754%	$130.3308	$130.33	$130.35	$130.30
Purchase #4	$72.42	6.589%	$77.1918	$77.19	$77.20	$77.20
Purchase #5	$90.33	11.710%	$100.9076	$100.91	$100.90	$100.90
Purchase #6	$237.39	5.865%	$251.3129	$251.31	$251.30	$251.30
Purchase #7	$83.44	12.485%	$93.8575	$93.86	$93.85	$93.90
7 purchase totals =	$1,021.57		$1,105.4795	$1,105.48	$1,105.50	$1,105.50