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	$47.52	11.806%	$53.1302	$53.13	$53.15	$53.10
Purchase #2	$194.73	8.604%	$211.4846	$211.48	$211.50	$211.50
Purchase #3	$202.54	6.368%	$215.4377	$215.44	$215.45	$215.40
Purchase #4	$164.84	12.323%	$185.1532	$185.15	$185.15	$185.20
Purchase #5	$62.60	4.293%	$65.2874	$65.29	$65.30	$65.30
Purchase #6	$145.43	3.317%	$150.2539	$150.25	$150.25	$150.30
Purchase #7	$225.68	9.389%	$246.8691	$246.87	$246.85	$246.90
7 purchase totals =	$1,043.34		$1,127.6161	$1,127.61	$1,127.65	$1,127.70