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	$192.65	9.479%	$210.9113	$210.91	$210.90	$210.90
Purchase #2	$230.74	6.390%	$245.4843	$245.48	$245.50	$245.50
Purchase #3	$75.75	4.704%	$79.3133	$79.31	$79.30	$79.30
Purchase #4	$10.45	7.780%	$11.263	$11.26	$11.25	$11.30
Purchase #5	$250.62	13.345%	$284.0652	$284.07	$284.05	$284.10
Purchase #6	$156.89	6.761%	$167.4973	$167.50	$167.50	$167.50
Purchase #7	$38.46	6.187%	$40.8395	$40.84	$40.85	$40.80
7 purchase totals =	$955.56		$1,039.3739	$1,039.37	$1,039.35	$1,039.40