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	$134.45	4.232%	$140.1399	$140.14	$140.15	$140.10
Purchase #2	$104.89	5.156%	$110.2981	$110.30	$110.30	$110.30
Purchase #3	$104.30	7.699%	$112.3301	$112.33	$112.35	$112.30
Purchase #4	$10.41	10.657%	$11.5194	$11.52	$11.50	$11.50
Purchase #5	$155.38	6.436%	$165.3803	$165.38	$165.40	$165.40
Purchase #6	$77.98	9.603%	$85.4684	$85.47	$85.45	$85.50
Purchase #7	$80.43	6.808%	$85.9057	$85.91	$85.90	$85.90
7 purchase totals =	$667.84		$711.0419	$711.05	$711.05	$711.00