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	$77.95	3.698%	$80.8326	$80.83	$80.85	$80.80
Purchase #2	$38.35	8.388%	$41.5668	$41.57	$41.55	$41.60
Purchase #3	$32.91	3.444%	$34.0434	$34.04	$34.05	$34.00
Purchase #4	$190.41	3.228%	$196.5564	$196.56	$196.55	$196.60
Purchase #5	$53.35	7.735%	$57.4766	$57.48	$57.50	$57.50
Purchase #6	$214.76	8.851%	$233.7684	$233.77	$233.75	$233.80
Purchase #7	$220.52	11.235%	$245.2954	$245.30	$245.30	$245.30
7 purchase totals =	$828.25		$889.5396	$889.55	$889.55	$889.60