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	$174.87	8.167%	$189.1516	$189.15	$189.15	$189.20
Purchase #2	$82.75	11.436%	$92.2133	$92.21	$92.20	$92.20
Purchase #3	$196.73	6.139%	$208.8073	$208.81	$208.80	$208.80
Purchase #4	$112.88	3.267%	$116.5678	$116.57	$116.55	$116.60
Purchase #5	$141.58	7.553%	$152.2735	$152.27	$152.25	$152.30
Purchase #6	$127.86	13.762%	$145.4561	$145.46	$145.45	$145.50
Purchase #7	$247.40	13.837%	$281.6327	$281.63	$281.65	$281.60
7 purchase totals =	$1,084.07		$1,186.1023	$1,186.10	$1,186.05	$1,186.20