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	$152.97	7.413%	$164.3097	$164.31	$164.30	$164.30
Purchase #2	$198.25	3.662%	$205.5099	$205.51	$205.50	$205.50
Purchase #3	$220.40	11.109%	$244.8842	$244.88	$244.90	$244.90
Purchase #4	$92.37	7.805%	$99.5795	$99.58	$99.60	$99.60
Purchase #5	$41.67	6.598%	$44.4194	$44.42	$44.40	$44.40
Purchase #6	$138.60	4.793%	$145.2431	$145.24	$145.25	$145.20
Purchase #7	$69.30	12.821%	$78.185	$78.19	$78.20	$78.20
7 purchase totals =	$913.56		$982.1308	$982.13	$982.15	$982.10