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	$150.46	9.516%	$164.7778	$164.78	$164.80	$164.80
Purchase #2	$203.90	10.359%	$225.022	$225.02	$225.00	$225.00
Purchase #3	$149.34	12.439%	$167.9164	$167.92	$167.90	$167.90
Purchase #4	$216.41	3.219%	$223.3762	$223.38	$223.40	$223.40
Purchase #5	$147.53	12.186%	$165.508	$165.51	$165.50	$165.50
Purchase #6	$127.73	4.102%	$132.9695	$132.97	$132.95	$133.00
Purchase #7	$103.25	11.153%	$114.7655	$114.77	$114.75	$114.80
7 purchase totals =	$1,098.62		$1,194.3354	$1,194.35	$1,194.30	$1,194.40