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	$210.73	6.184%	$223.7615	$223.76	$223.75	$223.80
Purchase #2	$172.99	10.162%	$190.5692	$190.57	$190.55	$190.60
Purchase #3	$137.98	12.750%	$155.5725	$155.57	$155.55	$155.60
Purchase #4	$78.88	6.776%	$84.2249	$84.22	$84.20	$84.20
Purchase #5	$165.45	4.155%	$172.3244	$172.32	$172.30	$172.30
Purchase #6	$111.60	11.623%	$124.5713	$124.57	$124.55	$124.60
Purchase #7	$203.75	9.697%	$223.5076	$223.51	$223.50	$223.50
7 purchase totals =	$1,081.38		$1,174.5314	$1,174.52	$1,174.40	$1,174.60