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	$125.32	11.819%	$140.1316	$140.13	$140.15	$140.10
Purchase #2	$219.36	11.299%	$244.1455	$244.15	$244.15	$244.10
Purchase #3	$136.39	11.586%	$152.1921	$152.19	$152.20	$152.20
Purchase #4	$242.50	6.707%	$258.7645	$258.76	$258.75	$258.80
Purchase #5	$31.63	4.378%	$33.0148	$33.01	$33.00	$33.00
Purchase #6	$103.81	13.367%	$117.6863	$117.69	$117.70	$117.70
Purchase #7	$65.61	10.300%	$72.3678	$72.37	$72.35	$72.40
7 purchase totals =	$924.62		$1,018.3026	$1,018.30	$1,018.30	$1,018.30