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	$126.48	3.175%	$130.4957	$130.50	$130.50	$130.50
Purchase #2	$229.71	10.263%	$253.2851	$253.29	$253.30	$253.30
Purchase #3	$16.57	12.364%	$18.6187	$18.62	$18.60	$18.60
Purchase #4	$45.43	4.598%	$47.5189	$47.52	$47.50	$47.50
Purchase #5	$65.64	10.498%	$72.5309	$72.53	$72.55	$72.50
Purchase #6	$220.49	7.299%	$236.5836	$236.58	$236.60	$236.60
Purchase #7	$111.46	6.214%	$118.3861	$118.39	$118.40	$118.40
7 purchase totals =	$815.78		$877.4190	$877.43	$877.45	$877.40