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	$32.38	13.748%	$36.8316	$36.83	$36.85	$36.80
Purchase #2	$67.52	8.759%	$73.4341	$73.43	$73.45	$73.40
Purchase #3	$101.70	12.601%	$114.5152	$114.52	$114.50	$114.50
Purchase #4	$25.75	6.255%	$27.3607	$27.36	$27.35	$27.40
Purchase #5	$53.41	10.395%	$58.962	$58.96	$58.95	$59.00
Purchase #6	$172.73	4.377%	$180.2904	$180.29	$180.30	$180.30
Purchase #7	$73.36	6.345%	$78.0147	$78.01	$78.00	$78.00
7 purchase totals =	$526.85		$569.4087	$569.40	$569.40	$569.40