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	$209.68	5.808%	$221.8582	$221.86	$221.85	$221.90
Purchase #2	$141.79	3.334%	$146.5173	$146.52	$146.50	$146.50
Purchase #3	$174.47	6.141%	$185.1842	$185.18	$185.20	$185.20
Purchase #4	$10.41	11.735%	$11.6316	$11.63	$11.65	$11.60
Purchase #5	$14.55	9.123%	$15.8774	$15.88	$15.90	$15.90
Purchase #6	$78.74	4.277%	$82.1077	$82.11	$82.10	$82.10
Purchase #7	$225.41	3.633%	$233.5991	$233.60	$233.60	$233.60
7 purchase totals =	$855.05		$896.7755	$896.78	$896.80	$896.80