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	$54.65	4.192%	$56.9409	$56.94	$56.95	$56.90
Purchase #2	$165.83	5.595%	$175.1082	$175.11	$175.10	$175.10
Purchase #3	$169.99	7.447%	$182.6492	$182.65	$182.65	$182.60
Purchase #4	$198.34	12.147%	$222.4324	$222.43	$222.45	$222.40
Purchase #5	$34.67	12.250%	$38.9171	$38.92	$38.90	$38.90
Purchase #6	$5.65	12.438%	$6.3527	$6.35	$6.35	$6.40
Purchase #7	$55.92	6.426%	$59.5134	$59.51	$59.50	$59.50
7 purchase totals =	$685.05		$741.9139	$741.91	$741.90	$741.80