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	$192.67	8.335%	$208.729	$208.73	$208.75	$208.70
Purchase #2	$123.65	5.399%	$130.3259	$130.33	$130.35	$130.30
Purchase #3	$51.45	11.815%	$57.5288	$57.53	$57.55	$57.50
Purchase #4	$231.82	11.799%	$259.1724	$259.17	$259.15	$259.20
Purchase #5	$7.60	11.824%	$8.4986	$8.50	$8.50	$8.50
Purchase #6	$87.96	3.324%	$90.8838	$90.88	$90.90	$90.90
Purchase #7	$217.80	12.245%	$244.4696	$244.47	$244.45	$244.50
7 purchase totals =	$912.95		$999.6081	$999.61	$999.65	$999.60