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	$163.69	12.562%	$184.2527	$184.25	$184.25	$184.30
Purchase #2	$164.65	4.643%	$172.2947	$172.29	$172.30	$172.30
Purchase #3	$69.38	13.602%	$78.8171	$78.82	$78.80	$78.80
Purchase #4	$31.56	11.229%	$35.1039	$35.10	$35.10	$35.10
Purchase #5	$109.49	12.777%	$123.4795	$123.48	$123.50	$123.50
Purchase #6	$178.86	13.445%	$202.9077	$202.91	$202.90	$202.90
Purchase #7	$187.38	4.625%	$196.0463	$196.05	$196.05	$196.00
7 purchase totals =	$905.01		$992.9019	$992.90	$992.90	$992.90