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	$99.77	10.584%	$110.3297	$110.33	$110.35	$110.30
Purchase #2	$106.78	12.254%	$119.8648	$119.86	$119.85	$119.90
Purchase #3	$169.25	11.340%	$188.443	$188.44	$188.45	$188.40
Purchase #4	$152.78	3.811%	$158.6024	$158.60	$158.60	$158.60
Purchase #5	$210.83	3.144%	$217.4585	$217.46	$217.45	$217.50
Purchase #6	$112.68	6.447%	$119.9445	$119.94	$119.95	$119.90
Purchase #7	$77.87	11.282%	$86.6553	$86.66	$86.65	$86.70
7 purchase totals =	$929.96		$1,001.2982	$1,001.29	$1,001.30	$1,001.30