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	$207.96	7.642%	$223.8523	$223.85	$223.85	$223.90
Purchase #2	$69.44	11.649%	$77.5291	$77.53	$77.55	$77.50
Purchase #3	$128.94	10.851%	$142.9313	$142.93	$142.95	$142.90
Purchase #4	$94.39	10.840%	$104.6219	$104.62	$104.60	$104.60
Purchase #5	$237.34	11.613%	$264.9023	$264.90	$264.90	$264.90
Purchase #6	$96.68	11.850%	$108.1366	$108.14	$108.15	$108.10
Purchase #7	$227.65	7.395%	$244.4847	$244.48	$244.50	$244.50
7 purchase totals =	$1,062.40		$1,166.4582	$1,166.45	$1,166.50	$1,166.40