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	$51.48	4.230%	$53.6576	$53.66	$53.65	$53.70
Purchase #2	$153.27	12.813%	$172.9085	$172.91	$172.90	$172.90
Purchase #3	$123.62	7.859%	$133.3353	$133.34	$133.35	$133.30
Purchase #4	$131.31	13.464%	$148.9896	$148.99	$149.00	$149.00
Purchase #5	$89.84	3.666%	$93.1335	$93.13	$93.15	$93.10
Purchase #6	$75.76	3.367%	$78.3108	$78.31	$78.30	$78.30
Purchase #7	$6.77	12.440%	$7.6122	$7.61	$7.60	$7.60
7 purchase totals =	$632.05		$687.9475	$687.95	$687.95	$687.90