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	$130.45	4.851%	$136.7781	$136.78	$136.80	$136.80
Purchase #2	$152.48	8.744%	$165.8129	$165.81	$165.80	$165.80
Purchase #3	$224.32	7.579%	$241.3212	$241.32	$241.30	$241.30
Purchase #4	$169.55	3.361%	$175.2486	$175.25	$175.25	$175.20
Purchase #5	$157.80	6.361%	$167.8377	$167.84	$167.85	$167.80
Purchase #6	$234.88	13.781%	$267.2488	$267.25	$267.25	$267.20
Purchase #7	$73.90	13.547%	$83.9112	$83.91	$83.90	$83.90
7 purchase totals =	$1,143.38		$1,238.1585	$1,238.16	$1,238.15	$1,238.00