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	$93.88	12.234%	$105.3653	$105.37	$105.35	$105.40
Purchase #2	$132.55	4.253%	$138.1874	$138.19	$138.20	$138.20
Purchase #3	$154.35	7.488%	$165.9077	$165.91	$165.90	$165.90
Purchase #4	$44.94	12.406%	$50.5153	$50.52	$50.50	$50.50
Purchase #5	$97.52	7.701%	$105.03	$105.03	$105.05	$105.00
Purchase #6	$111.34	7.736%	$119.9533	$119.95	$119.95	$120.00
Purchase #7	$98.53	5.494%	$103.9432	$103.94	$103.95	$103.90
7 purchase totals =	$733.11		$788.9022	$788.91	$788.90	$788.90