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	$129.70	5.231%	$136.4846	$136.48	$136.50	$136.50
Purchase #2	$54.61	13.677%	$62.079	$62.08	$62.10	$62.10
Purchase #3	$26.69	11.534%	$29.7684	$29.77	$29.75	$29.80
Purchase #4	$182.41	7.726%	$196.503	$196.50	$196.50	$196.50
Purchase #5	$61.34	10.590%	$67.8359	$67.84	$67.85	$67.80
Purchase #6	$25.66	13.345%	$29.0843	$29.08	$29.10	$29.10
Purchase #7	$185.42	11.436%	$206.6246	$206.62	$206.60	$206.60
7 purchase totals =	$665.83		$728.3798	$728.37	$728.40	$728.40