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	$230.93	6.324%	$245.534	$245.53	$245.55	$245.50
Purchase #2	$66.57	5.534%	$70.254	$70.25	$70.25	$70.30
Purchase #3	$184.80	8.399%	$200.3214	$200.32	$200.30	$200.30
Purchase #4	$128.58	3.780%	$133.4403	$133.44	$133.45	$133.40
Purchase #5	$53.28	8.686%	$57.9079	$57.91	$57.90	$57.90
Purchase #6	$119.54	9.741%	$131.1844	$131.18	$131.20	$131.20
Purchase #7	$219.50	12.498%	$246.9331	$246.93	$246.95	$246.90
7 purchase totals =	$1,003.20		$1,085.5751	$1,085.56	$1,085.60	$1,085.50