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	$131.66	4.468%	$137.5426	$137.54	$137.55	$137.50
Purchase #2	$242.91	3.108%	$250.4596	$250.46	$250.45	$250.50
Purchase #3	$90.43	7.122%	$96.8704	$96.87	$96.85	$96.90
Purchase #4	$167.78	7.845%	$180.9423	$180.94	$180.95	$180.90
Purchase #5	$202.96	10.137%	$223.5341	$223.53	$223.55	$223.50
Purchase #6	$52.40	4.859%	$54.9461	$54.95	$54.95	$54.90
Purchase #7	$131.88	4.810%	$138.2234	$138.22	$138.20	$138.20
7 purchase totals =	$1,020.02		$1,082.5185	$1,082.51	$1,082.50	$1,082.40