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	$218.83	8.693%	$237.8529	$237.85	$237.85	$237.90
Purchase #2	$87.94	4.292%	$91.7144	$91.71	$91.70	$91.70
Purchase #3	$102.31	4.142%	$106.5477	$106.55	$106.55	$106.50
Purchase #4	$73.32	8.780%	$79.7575	$79.76	$79.75	$79.80
Purchase #5	$203.91	9.306%	$222.8859	$222.89	$222.90	$222.90
Purchase #6	$158.30	3.833%	$164.3676	$164.37	$164.35	$164.40
Purchase #7	$157.72	4.579%	$164.942	$164.94	$164.95	$164.90
7 purchase totals =	$1,002.33		$1,068.0680	$1,068.07	$1,068.05	$1,068.10