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	$243.86	7.722%	$262.6909	$262.69	$262.70	$262.70
Purchase #2	$179.32	7.306%	$192.4211	$192.42	$192.40	$192.40
Purchase #3	$28.74	13.489%	$32.6167	$32.62	$32.60	$32.60
Purchase #4	$100.91	6.239%	$107.2058	$107.21	$107.20	$107.20
Purchase #5	$225.95	7.365%	$242.5912	$242.59	$242.60	$242.60
Purchase #6	$57.94	6.158%	$61.5079	$61.51	$61.50	$61.50
Purchase #7	$187.61	5.850%	$198.5852	$198.59	$198.60	$198.60
7 purchase totals =	$1,024.33		$1,097.6188	$1,097.63	$1,097.60	$1,097.60