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	$35.39	6.727%	$37.7707	$37.77	$37.75	$37.80
Purchase #2	$144.83	4.451%	$151.2764	$151.28	$151.30	$151.30
Purchase #3	$172.49	5.511%	$181.9959	$182.00	$182.00	$182.00
Purchase #4	$59.82	6.405%	$63.6515	$63.65	$63.65	$63.70
Purchase #5	$96.71	6.680%	$103.1702	$103.17	$103.15	$103.20
Purchase #6	$169.93	4.817%	$178.1155	$178.12	$178.10	$178.10
Purchase #7	$214.59	13.502%	$243.5639	$243.56	$243.55	$243.60
7 purchase totals =	$893.76		$959.5441	$959.55	$959.50	$959.70