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	$151.39	7.367%	$162.5429	$162.54	$162.55	$162.50
Purchase #2	$89.51	11.395%	$99.7097	$99.71	$99.70	$99.70
Purchase #3	$22.30	3.367%	$23.0508	$23.05	$23.05	$23.10
Purchase #4	$152.73	7.385%	$164.0091	$164.01	$164.00	$164.00
Purchase #5	$197.90	3.854%	$205.5271	$205.53	$205.55	$205.50
Purchase #6	$75.65	4.351%	$78.9415	$78.94	$78.95	$78.90
Purchase #7	$31.50	12.388%	$35.4022	$35.40	$35.40	$35.40
7 purchase totals =	$720.98		$769.1833	$769.18	$769.20	$769.10