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	$113.84	9.117%	$124.2188	$124.22	$124.20	$124.20
Purchase #2	$142.43	5.113%	$149.7124	$149.71	$149.70	$149.70
Purchase #3	$88.57	4.689%	$92.723	$92.72	$92.70	$92.70
Purchase #4	$167.88	3.116%	$173.1111	$173.11	$173.10	$173.10
Purchase #5	$140.84	7.404%	$151.2678	$151.27	$151.25	$151.30
Purchase #6	$241.31	5.833%	$255.3856	$255.39	$255.40	$255.40
Purchase #7	$198.86	9.678%	$218.1057	$218.11	$218.10	$218.10
7 purchase totals =	$1,093.73		$1,164.5244	$1,164.53	$1,164.45	$1,164.50