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	$85.81	4.663%	$89.8113	$89.81	$89.80	$89.80
Purchase #2	$114.74	4.518%	$119.924	$119.92	$119.90	$119.90
Purchase #3	$164.42	4.751%	$172.2316	$172.23	$172.25	$172.20
Purchase #4	$57.58	13.680%	$65.4569	$65.46	$65.45	$65.50
Purchase #5	$10.67	7.554%	$11.476	$11.48	$11.50	$11.50
Purchase #6	$45.39	3.568%	$47.0095	$47.01	$47.00	$47.00
Purchase #7	$108.50	6.228%	$115.2574	$115.26	$115.25	$115.30
7 purchase totals =	$587.11		$621.1667	$621.17	$621.15	$621.20