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	$113.93	13.818%	$129.6728	$129.67	$129.65	$129.70
Purchase #2	$219.53	4.556%	$229.5318	$229.53	$229.55	$229.50
Purchase #3	$150.99	13.178%	$170.8875	$170.89	$170.90	$170.90
Purchase #4	$53.91	10.411%	$59.5226	$59.52	$59.50	$59.50
Purchase #5	$246.75	7.377%	$264.9527	$264.95	$264.95	$265.00
Purchase #6	$227.39	3.301%	$234.8961	$234.90	$234.90	$234.90
Purchase #7	$23.83	6.816%	$25.4543	$25.45	$25.45	$25.50
7 purchase totals =	$1,036.33		$1,114.9178	$1,114.91	$1,114.90	$1,115.00