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	$123.85	7.871%	$133.5982	$133.60	$133.60	$133.60
Purchase #2	$180.47	7.777%	$194.5052	$194.51	$194.50	$194.50
Purchase #3	$230.83	8.654%	$250.806	$250.81	$250.80	$250.80
Purchase #4	$37.32	4.816%	$39.1173	$39.12	$39.10	$39.10
Purchase #5	$175.25	13.321%	$198.5951	$198.60	$198.60	$198.60
Purchase #6	$129.90	13.597%	$147.5625	$147.56	$147.55	$147.60
Purchase #7	$132.29	10.471%	$146.1421	$146.14	$146.15	$146.10
7 purchase totals =	$1,009.91		$1,110.3264	$1,110.34	$1,110.30	$1,110.30