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	$63.34	3.103%	$65.3054	$65.31	$65.30	$65.30
Purchase #2	$201.90	12.521%	$227.1799	$227.18	$227.20	$227.20
Purchase #3	$43.48	6.576%	$46.3392	$46.34	$46.35	$46.30
Purchase #4	$243.55	4.829%	$255.311	$255.31	$255.30	$255.30
Purchase #5	$223.51	9.532%	$244.815	$244.82	$244.80	$244.80
Purchase #6	$49.37	10.226%	$54.4186	$54.42	$54.40	$54.40
Purchase #7	$174.34	3.672%	$180.7418	$180.74	$180.75	$180.70
7 purchase totals =	$999.49		$1,074.1109	$1,074.12	$1,074.10	$1,074.00