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	$61.61	8.482%	$66.8358	$66.84	$66.85	$66.80
Purchase #2	$96.35	6.194%	$102.3179	$102.32	$102.30	$102.30
Purchase #3	$83.72	8.234%	$90.6135	$90.61	$90.60	$90.60
Purchase #4	$152.80	12.535%	$171.9535	$171.95	$171.95	$172.00
Purchase #5	$245.87	4.148%	$256.0687	$256.07	$256.05	$256.10
Purchase #6	$142.41	4.533%	$148.8654	$148.87	$148.85	$148.90
Purchase #7	$87.70	10.157%	$96.6077	$96.61	$96.60	$96.60
7 purchase totals =	$870.46		$933.2625	$933.27	$933.20	$933.30