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	$100.94	8.795%	$109.8177	$109.82	$109.80	$109.80
Purchase #2	$179.60	9.110%	$195.9616	$195.96	$195.95	$196.00
Purchase #3	$56.31	8.616%	$61.1617	$61.16	$61.15	$61.20
Purchase #4	$45.45	12.105%	$50.9517	$50.95	$50.95	$51.00
Purchase #5	$70.44	6.853%	$75.2673	$75.27	$75.25	$75.30
Purchase #6	$68.30	3.269%	$70.5327	$70.53	$70.55	$70.50
Purchase #7	$210.69	3.123%	$217.2698	$217.27	$217.25	$217.30
7 purchase totals =	$731.73		$780.9625	$780.96	$780.90	$781.10