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	$32.77	3.301%	$33.8517	$33.85	$33.85	$33.90
Purchase #2	$68.71	13.728%	$78.1425	$78.14	$78.15	$78.10
Purchase #3	$199.64	8.259%	$216.1283	$216.13	$216.15	$216.10
Purchase #4	$93.56	8.417%	$101.4349	$101.43	$101.45	$101.40
Purchase #5	$227.51	4.853%	$238.5511	$238.55	$238.55	$238.60
Purchase #6	$120.57	8.763%	$131.1355	$131.14	$131.15	$131.10
Purchase #7	$45.44	8.564%	$49.3315	$49.33	$49.35	$49.30
7 purchase totals =	$788.20		$848.5755	$848.57	$848.65	$848.50