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	$227.54	8.111%	$245.9958	$246.00	$246.00	$246.00
Purchase #2	$44.47	13.450%	$50.4512	$50.45	$50.45	$50.50
Purchase #3	$209.72	8.483%	$227.5105	$227.51	$227.50	$227.50
Purchase #4	$161.39	3.731%	$167.4115	$167.41	$167.40	$167.40
Purchase #5	$250.44	9.221%	$273.5331	$273.53	$273.55	$273.50
Purchase #6	$127.77	11.664%	$142.6731	$142.67	$142.65	$142.70
Purchase #7	$54.61	13.548%	$62.0086	$62.01	$62.00	$62.00
7 purchase totals =	$1,075.94		$1,169.5838	$1,169.58	$1,169.55	$1,169.60