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	$65.46	10.595%	$72.3955	$72.40	$72.40	$72.40
Purchase #2	$87.49	13.361%	$99.1795	$99.18	$99.20	$99.20
Purchase #3	$140.52	3.115%	$144.8972	$144.90	$144.90	$144.90
Purchase #4	$243.79	5.850%	$258.0517	$258.05	$258.05	$258.10
Purchase #5	$35.47	11.520%	$39.5561	$39.56	$39.55	$39.60
Purchase #6	$100.41	3.327%	$103.7506	$103.75	$103.75	$103.80
Purchase #7	$172.82	9.560%	$189.3416	$189.34	$189.35	$189.30
7 purchase totals =	$845.96		$907.1722	$907.18	$907.20	$907.30