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	$76.65	8.748%	$83.3553	$83.36	$83.35	$83.40
Purchase #2	$179.42	6.824%	$191.6636	$191.66	$191.65	$191.70
Purchase #3	$112.85	5.531%	$119.0917	$119.09	$119.10	$119.10
Purchase #4	$200.28	11.235%	$222.7815	$222.78	$222.80	$222.80
Purchase #5	$64.89	12.375%	$72.9201	$72.92	$72.90	$72.90
Purchase #6	$216.47	6.375%	$230.27	$230.27	$230.25	$230.30
Purchase #7	$243.66	10.779%	$269.9241	$269.92	$269.90	$269.90
7 purchase totals =	$1,094.22		$1,190.0063	$1,190.00	$1,189.95	$1,190.10