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	$61.83	8.864%	$67.3106	$67.31	$67.30	$67.30
Purchase #2	$90.31	4.572%	$94.439	$94.44	$94.45	$94.40
Purchase #3	$243.30	5.130%	$255.7813	$255.78	$255.80	$255.80
Purchase #4	$195.39	11.624%	$218.1021	$218.10	$218.10	$218.10
Purchase #5	$226.54	7.417%	$243.3425	$243.34	$243.35	$243.30
Purchase #6	$217.54	12.703%	$245.1741	$245.17	$245.15	$245.20
Purchase #7	$199.56	9.192%	$217.9036	$217.90	$217.90	$217.90
7 purchase totals =	$1,234.47		$1,342.0532	$1,342.04	$1,342.05	$1,342.00