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	$101.54	11.743%	$113.4638	$113.46	$113.45	$113.50
Purchase #2	$209.43	3.212%	$216.1569	$216.16	$216.15	$216.20
Purchase #3	$110.63	11.650%	$123.5184	$123.52	$123.50	$123.50
Purchase #4	$217.33	10.171%	$239.4346	$239.43	$239.45	$239.40
Purchase #5	$48.40	10.152%	$53.3136	$53.31	$53.30	$53.30
Purchase #6	$60.49	3.260%	$62.462	$62.46	$62.45	$62.50
Purchase #7	$127.67	6.648%	$136.1575	$136.16	$136.15	$136.20
7 purchase totals =	$875.49		$944.5068	$944.50	$944.45	$944.60