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	$196.40	10.276%	$216.5821	$216.58	$216.60	$216.60
Purchase #2	$135.52	7.720%	$145.9821	$145.98	$146.00	$146.00
Purchase #3	$127.26	3.488%	$131.6988	$131.70	$131.70	$131.70
Purchase #4	$223.71	12.349%	$251.3359	$251.34	$251.35	$251.30
Purchase #5	$80.50	11.605%	$89.842	$89.84	$89.85	$89.80
Purchase #6	$47.87	12.731%	$53.9643	$53.96	$53.95	$54.00
Purchase #7	$221.82	13.362%	$251.4596	$251.46	$251.45	$251.50
7 purchase totals =	$1,033.08		$1,140.8648	$1,140.86	$1,140.90	$1,140.90