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	$120.27	8.603%	$130.6168	$130.62	$130.60	$130.60
Purchase #2	$172.94	3.529%	$179.0431	$179.04	$179.05	$179.00
Purchase #3	$141.89	3.484%	$146.8334	$146.83	$146.85	$146.80
Purchase #4	$109.32	13.828%	$124.4368	$124.44	$124.45	$124.40
Purchase #5	$233.53	6.629%	$249.0107	$249.01	$249.00	$249.00
Purchase #6	$148.75	9.117%	$162.3115	$162.31	$162.30	$162.30
Purchase #7	$109.31	12.618%	$123.1027	$123.10	$123.10	$123.10
7 purchase totals =	$1,036.01		$1,115.3550	$1,115.35	$1,115.35	$1,115.20