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	$94.26	13.193%	$106.6957	$106.70	$106.70	$106.70
Purchase #2	$125.79	4.825%	$131.8594	$131.86	$131.85	$131.90
Purchase #3	$130.75	10.836%	$144.9181	$144.92	$144.90	$144.90
Purchase #4	$129.73	12.554%	$146.0163	$146.02	$146.00	$146.00
Purchase #5	$166.33	7.781%	$179.2721	$179.27	$179.25	$179.30
Purchase #6	$130.85	7.233%	$140.3144	$140.31	$140.30	$140.30
Purchase #7	$177.49	10.641%	$196.3767	$196.38	$196.40	$196.40
7 purchase totals =	$955.20		$1,045.4527	$1,045.46	$1,045.40	$1,045.50