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	$138.45	3.115%	$142.7627	$142.76	$142.75	$142.80
Purchase #2	$145.38	11.485%	$162.0769	$162.08	$162.10	$162.10
Purchase #3	$207.42	7.353%	$222.6716	$222.67	$222.65	$222.70
Purchase #4	$238.59	6.240%	$253.478	$253.48	$253.50	$253.50
Purchase #5	$132.69	10.478%	$146.5933	$146.59	$146.60	$146.60
Purchase #6	$81.56	11.742%	$91.1368	$91.14	$91.15	$91.10
Purchase #7	$71.60	7.705%	$77.1168	$77.12	$77.10	$77.10
7 purchase totals =	$1,015.69		$1,095.8361	$1,095.84	$1,095.85	$1,095.90