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	$13.88	3.104%	$14.3108	$14.31	$14.30	$14.30
Purchase #2	$52.72	13.643%	$59.9126	$59.91	$59.90	$59.90
Purchase #3	$184.48	5.239%	$194.1449	$194.14	$194.15	$194.10
Purchase #4	$202.38	7.176%	$216.9028	$216.90	$216.90	$216.90
Purchase #5	$90.79	8.598%	$98.5961	$98.60	$98.60	$98.60
Purchase #6	$238.33	5.110%	$250.5087	$250.51	$250.50	$250.50
Purchase #7	$110.70	7.799%	$119.3335	$119.33	$119.35	$119.30
7 purchase totals =	$893.28		$953.7094	$953.70	$953.70	$953.60