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	$186.50	13.411%	$211.5115	$211.51	$211.50	$211.50
Purchase #2	$191.63	7.785%	$206.5484	$206.55	$206.55	$206.50
Purchase #3	$55.29	7.279%	$59.3146	$59.31	$59.30	$59.30
Purchase #4	$50.36	13.757%	$57.288	$57.29	$57.30	$57.30
Purchase #5	$16.86	9.679%	$18.4919	$18.49	$18.50	$18.50
Purchase #6	$40.75	5.270%	$42.8975	$42.90	$42.90	$42.90
Purchase #7	$127.33	7.821%	$137.2885	$137.29	$137.30	$137.30
7 purchase totals =	$668.72		$733.3404	$733.34	$733.35	$733.30