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	$65.49	10.199%	$72.1693	$72.17	$72.15	$72.20
Purchase #2	$85.46	8.129%	$92.407	$92.41	$92.40	$92.40
Purchase #3	$17.59	7.309%	$18.8757	$18.88	$18.90	$18.90
Purchase #4	$160.63	7.301%	$172.3576	$172.36	$172.35	$172.40
Purchase #5	$113.29	3.212%	$116.9289	$116.93	$116.95	$116.90
Purchase #6	$144.43	3.869%	$150.018	$150.02	$150.00	$150.00
Purchase #7	$17.61	10.865%	$19.5233	$19.52	$19.50	$19.50
7 purchase totals =	$604.50		$642.2798	$642.29	$642.25	$642.30