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	$73.56	11.793%	$82.2349	$82.23	$82.25	$82.20
Purchase #2	$246.57	3.150%	$254.337	$254.34	$254.35	$254.30
Purchase #3	$87.57	8.662%	$95.1553	$95.16	$95.15	$95.20
Purchase #4	$24.29	3.623%	$25.17	$25.17	$25.15	$25.20
Purchase #5	$172.69	9.381%	$188.89	$188.89	$188.90	$188.90
Purchase #6	$43.38	9.366%	$47.443	$47.44	$47.45	$47.40
Purchase #7	$200.31	11.592%	$223.5299	$223.53	$223.55	$223.50
7 purchase totals =	$848.37		$916.7601	$916.76	$916.80	$916.70