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	$126.50	10.192%	$139.3929	$139.39	$139.40	$139.40
Purchase #2	$79.87	4.589%	$83.5352	$83.54	$83.55	$83.50
Purchase #3	$145.45	4.479%	$151.9647	$151.96	$151.95	$152.00
Purchase #4	$72.69	4.859%	$76.222	$76.22	$76.20	$76.20
Purchase #5	$46.55	11.136%	$51.7338	$51.73	$51.75	$51.70
Purchase #6	$187.69	11.144%	$208.6062	$208.61	$208.60	$208.60
Purchase #7	$43.34	10.787%	$48.0151	$48.02	$48.00	$48.00
7 purchase totals =	$702.09		$759.4699	$759.47	$759.45	$759.40