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	$149.64	11.285%	$166.5269	$166.53	$166.55	$166.50
Purchase #2	$31.41	6.848%	$33.561	$33.56	$33.55	$33.60
Purchase #3	$59.30	10.483%	$65.5164	$65.52	$65.50	$65.50
Purchase #4	$36.42	10.124%	$40.1072	$40.11	$40.10	$40.10
Purchase #5	$39.89	9.393%	$43.6369	$43.64	$43.65	$43.60
Purchase #6	$140.50	10.154%	$154.7664	$154.77	$154.75	$154.80
Purchase #7	$235.25	13.223%	$266.3571	$266.36	$266.35	$266.40
7 purchase totals =	$692.41		$770.4719	$770.49	$770.45	$770.50