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	$230.47	7.594%	$247.9719	$247.97	$247.95	$248.00
Purchase #2	$69.56	5.813%	$73.6035	$73.60	$73.60	$73.60
Purchase #3	$10.46	12.533%	$11.771	$11.77	$11.75	$11.80
Purchase #4	$244.90	13.781%	$278.6497	$278.65	$278.65	$278.60
Purchase #5	$88.27	13.708%	$100.3701	$100.37	$100.35	$100.40
Purchase #6	$145.90	13.298%	$165.3018	$165.30	$165.30	$165.30
Purchase #7	$28.82	8.669%	$31.3184	$31.32	$31.30	$31.30
7 purchase totals =	$818.38		$908.9864	$908.98	$908.90	$909.00