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	$198.28	13.859%	$225.7596	$225.76	$225.75	$225.80
Purchase #2	$125.88	12.475%	$141.5835	$141.58	$141.60	$141.60
Purchase #3	$57.40	8.676%	$62.38	$62.38	$62.40	$62.40
Purchase #4	$62.56	7.554%	$67.2858	$67.29	$67.30	$67.30
Purchase #5	$45.59	3.770%	$47.3087	$47.31	$47.30	$47.30
Purchase #6	$110.84	5.822%	$117.2931	$117.29	$117.30	$117.30
Purchase #7	$128.94	13.701%	$146.6061	$146.61	$146.60	$146.60
7 purchase totals =	$729.49		$808.2168	$808.22	$808.25	$808.30