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	$168.55	3.615%	$174.6431	$174.64	$174.65	$174.60
Purchase #2	$201.82	9.745%	$221.4874	$221.49	$221.50	$221.50
Purchase #3	$161.48	5.577%	$170.4857	$170.49	$170.50	$170.50
Purchase #4	$151.88	13.385%	$172.2091	$172.21	$172.20	$172.20
Purchase #5	$12.51	7.273%	$13.4199	$13.42	$13.40	$13.40
Purchase #6	$231.67	13.851%	$263.7586	$263.76	$263.75	$263.80
Purchase #7	$185.46	5.746%	$196.1165	$196.12	$196.10	$196.10
7 purchase totals =	$1,113.37		$1,212.1203	$1,212.13	$1,212.10	$1,212.10