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	$75.31	11.137%	$83.6973	$83.70	$83.70	$83.70
Purchase #2	$136.51	11.155%	$151.7377	$151.74	$151.75	$151.70
Purchase #3	$118.79	10.432%	$131.1822	$131.18	$131.20	$131.20
Purchase #4	$55.41	7.570%	$59.6045	$59.60	$59.60	$59.60
Purchase #5	$190.61	3.362%	$197.0183	$197.02	$197.00	$197.00
Purchase #6	$80.44	9.407%	$88.007	$88.01	$88.00	$88.00
Purchase #7	$103.45	12.346%	$116.2219	$116.22	$116.20	$116.20
7 purchase totals =	$760.52		$827.4689	$827.47	$827.45	$827.40