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	$222.57	3.740%	$230.8941	$230.89	$230.90	$230.90
Purchase #2	$90.69	3.104%	$93.505	$93.51	$93.50	$93.50
Purchase #3	$117.33	5.212%	$123.4452	$123.45	$123.45	$123.40
Purchase #4	$118.40	6.620%	$126.2381	$126.24	$126.25	$126.20
Purchase #5	$53.67	3.261%	$55.4202	$55.42	$55.40	$55.40
Purchase #6	$219.27	7.843%	$236.4673	$236.47	$236.45	$236.50
Purchase #7	$69.58	12.409%	$78.2142	$78.21	$78.20	$78.20
7 purchase totals =	$891.51		$944.1841	$944.19	$944.15	$944.10