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	$244.82	4.245%	$255.2126	$255.21	$255.20	$255.20
Purchase #2	$115.71	9.830%	$127.0843	$127.08	$127.10	$127.10
Purchase #3	$41.81	11.687%	$46.6963	$46.70	$46.70	$46.70
Purchase #4	$115.89	7.813%	$124.9445	$124.94	$124.95	$124.90
Purchase #5	$197.75	13.486%	$224.4186	$224.42	$224.40	$224.40
Purchase #6	$157.78	10.595%	$174.4968	$174.50	$174.50	$174.50
Purchase #7	$80.74	6.367%	$85.8807	$85.88	$85.90	$85.90
7 purchase totals =	$954.50		$1,038.7338	$1,038.73	$1,038.75	$1,038.70