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	$108.69	9.400%	$118.9069	$118.91	$118.90	$118.90
Purchase #2	$188.61	12.455%	$212.1014	$212.10	$212.10	$212.10
Purchase #3	$20.94	5.203%	$22.0295	$22.03	$22.05	$22.00
Purchase #4	$84.86	9.482%	$92.9064	$92.91	$92.90	$92.90
Purchase #5	$194.26	11.651%	$216.8932	$216.89	$216.90	$216.90
Purchase #6	$56.63	10.326%	$62.4776	$62.48	$62.50	$62.50
Purchase #7	$119.34	6.537%	$127.1413	$127.14	$127.15	$127.10
7 purchase totals =	$773.33		$852.4563	$852.46	$852.50	$852.40