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	$162.64	10.874%	$180.3255	$180.33	$180.35	$180.30
Purchase #2	$38.91	8.122%	$42.0703	$42.07	$42.05	$42.10
Purchase #3	$30.61	5.589%	$32.3208	$32.32	$32.30	$32.30
Purchase #4	$56.96	12.229%	$63.9256	$63.93	$63.95	$63.90
Purchase #5	$126.86	13.548%	$144.047	$144.05	$144.05	$144.00
Purchase #6	$225.49	7.659%	$242.7603	$242.76	$242.75	$242.80
Purchase #7	$53.39	8.106%	$57.7178	$57.72	$57.70	$57.70
7 purchase totals =	$694.86		$763.1673	$763.18	$763.15	$763.10