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	$168.45	6.507%	$179.411	$179.41	$179.40	$179.40
Purchase #2	$40.89	9.544%	$44.7925	$44.79	$44.80	$44.80
Purchase #3	$42.75	8.850%	$46.5334	$46.53	$46.55	$46.50
Purchase #4	$42.48	7.165%	$45.5237	$45.52	$45.50	$45.50
Purchase #5	$62.97	11.599%	$70.2739	$70.27	$70.25	$70.30
Purchase #6	$10.86	8.227%	$11.7535	$11.75	$11.75	$11.80
Purchase #7	$200.85	12.653%	$226.2636	$226.26	$226.25	$226.30
7 purchase totals =	$569.25		$624.5516	$624.53	$624.50	$624.60