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	$130.72	7.353%	$140.3318	$140.33	$140.35	$140.30
Purchase #2	$78.61	9.574%	$86.1361	$86.14	$86.15	$86.10
Purchase #3	$118.55	11.338%	$131.9912	$131.99	$132.00	$132.00
Purchase #4	$54.59	13.361%	$61.8838	$61.88	$61.90	$61.90
Purchase #5	$61.43	13.135%	$69.4988	$69.50	$69.50	$69.50
Purchase #6	$31.32	4.488%	$32.7256	$32.73	$32.75	$32.70
Purchase #7	$100.27	10.421%	$110.7191	$110.72	$110.70	$110.70
7 purchase totals =	$575.49		$633.2864	$633.29	$633.35	$633.20