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	$83.63	7.453%	$89.8629	$89.86	$89.85	$89.90
Purchase #2	$90.26	13.141%	$102.1211	$102.12	$102.10	$102.10
Purchase #3	$82.78	3.796%	$85.9223	$85.92	$85.90	$85.90
Purchase #4	$37.95	13.340%	$43.0125	$43.01	$43.00	$43.00
Purchase #5	$159.78	8.530%	$173.4092	$173.41	$173.40	$173.40
Purchase #6	$207.60	5.769%	$219.5764	$219.58	$219.60	$219.60
Purchase #7	$217.48	6.788%	$232.2425	$232.24	$232.25	$232.20
7 purchase totals =	$879.48		$946.1469	$946.14	$946.10	$946.10