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	$162.72	11.874%	$182.0414	$182.04	$182.05	$182.00
Purchase #2	$72.81	3.476%	$75.3409	$75.34	$75.35	$75.30
Purchase #3	$86.25	8.777%	$93.8202	$93.82	$93.80	$93.80
Purchase #4	$88.86	13.360%	$100.7317	$100.73	$100.75	$100.70
Purchase #5	$36.48	10.737%	$40.3969	$40.40	$40.40	$40.40
Purchase #6	$96.61	8.132%	$104.4663	$104.47	$104.45	$104.50
Purchase #7	$195.98	4.335%	$204.4757	$204.48	$204.50	$204.50
7 purchase totals =	$739.71		$801.2731	$801.28	$801.30	$801.20