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	$153.39	8.146%	$165.8851	$165.89	$165.90	$165.90
Purchase #2	$16.25	7.357%	$17.4455	$17.45	$17.45	$17.40
Purchase #3	$166.87	11.394%	$185.8832	$185.88	$185.90	$185.90
Purchase #4	$105.40	7.108%	$112.8918	$112.89	$112.90	$112.90
Purchase #5	$69.41	9.415%	$75.945	$75.95	$75.95	$75.90
Purchase #6	$43.58	11.388%	$48.5429	$48.54	$48.55	$48.50
Purchase #7	$127.63	13.696%	$145.1102	$145.11	$145.10	$145.10
7 purchase totals =	$682.53		$751.7037	$751.71	$751.75	$751.60