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	$102.48	8.560%	$111.2523	$111.25	$111.25	$111.30
Purchase #2	$193.31	9.203%	$211.1003	$211.10	$211.10	$211.10
Purchase #3	$134.60	4.359%	$140.4672	$140.47	$140.45	$140.50
Purchase #4	$10.74	13.223%	$12.1602	$12.16	$12.15	$12.20
Purchase #5	$137.75	11.513%	$153.6092	$153.61	$153.60	$153.60
Purchase #6	$227.89	12.674%	$256.7728	$256.77	$256.75	$256.80
Purchase #7	$42.76	9.135%	$46.6661	$46.67	$46.65	$46.70
7 purchase totals =	$849.53		$932.0281	$932.03	$931.95	$932.20