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	$48.67	8.247%	$52.6838	$52.68	$52.70	$52.70
Purchase #2	$237.74	7.187%	$254.8264	$254.83	$254.85	$254.80
Purchase #3	$80.66	12.140%	$90.4521	$90.45	$90.45	$90.50
Purchase #4	$232.91	9.655%	$255.3975	$255.40	$255.40	$255.40
Purchase #5	$38.68	12.268%	$43.4253	$43.43	$43.45	$43.40
Purchase #6	$242.34	3.488%	$250.7928	$250.79	$250.80	$250.80
Purchase #7	$147.64	7.448%	$158.6362	$158.64	$158.65	$158.60
7 purchase totals =	$1,028.64		$1,106.2141	$1,106.22	$1,106.30	$1,106.20