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	$82.85	5.675%	$87.5517	$87.55	$87.55	$87.60
Purchase #2	$103.95	7.282%	$111.5196	$111.52	$111.50	$111.50
Purchase #3	$233.67	12.683%	$263.3064	$263.31	$263.30	$263.30
Purchase #4	$34.85	12.408%	$39.1742	$39.17	$39.15	$39.20
Purchase #5	$98.58	6.653%	$105.1385	$105.14	$105.15	$105.10
Purchase #6	$200.80	10.275%	$221.4322	$221.43	$221.45	$221.40
Purchase #7	$195.42	3.502%	$202.2636	$202.26	$202.25	$202.30
7 purchase totals =	$950.12		$1,030.3862	$1,030.38	$1,030.35	$1,030.40