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	$202.27	10.536%	$223.5812	$223.58	$223.60	$223.60
Purchase #2	$165.81	7.668%	$178.5243	$178.52	$178.50	$178.50
Purchase #3	$9.66	11.605%	$10.781	$10.78	$10.80	$10.80
Purchase #4	$131.50	11.276%	$146.3279	$146.33	$146.35	$146.30
Purchase #5	$21.38	11.817%	$23.9065	$23.91	$23.90	$23.90
Purchase #6	$145.74	4.774%	$152.6976	$152.70	$152.70	$152.70
Purchase #7	$76.51	3.138%	$78.9109	$78.91	$78.90	$78.90
7 purchase totals =	$752.87		$814.7294	$814.73	$814.75	$814.70