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	$174.90	11.302%	$194.6672	$194.67	$194.65	$194.70
Purchase #2	$216.83	3.180%	$223.7252	$223.73	$223.75	$223.70
Purchase #3	$174.36	13.243%	$197.4505	$197.45	$197.45	$197.50
Purchase #4	$110.84	11.358%	$123.4292	$123.43	$123.45	$123.40
Purchase #5	$103.52	4.846%	$108.5366	$108.54	$108.55	$108.50
Purchase #6	$200.46	4.714%	$209.9097	$209.91	$209.90	$209.90
Purchase #7	$70.49	4.712%	$73.8115	$73.81	$73.80	$73.80
7 purchase totals =	$1,051.40		$1,131.5299	$1,131.54	$1,131.55	$1,131.50