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	$71.73	8.695%	$77.9669	$77.97	$77.95	$78.00
Purchase #2	$37.98	7.348%	$40.7708	$40.77	$40.75	$40.80
Purchase #3	$64.79	5.151%	$68.1273	$68.13	$68.15	$68.10
Purchase #4	$129.82	11.351%	$144.5559	$144.56	$144.55	$144.60
Purchase #5	$167.90	3.204%	$173.2795	$173.28	$173.30	$173.30
Purchase #6	$50.70	10.178%	$55.8602	$55.86	$55.85	$55.90
Purchase #7	$164.49	4.427%	$171.772	$171.77	$171.75	$171.80
7 purchase totals =	$687.41		$732.3326	$732.34	$732.30	$732.50