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	$184.90	6.510%	$196.937	$196.94	$196.95	$196.90
Purchase #2	$108.85	13.450%	$123.4903	$123.49	$123.50	$123.50
Purchase #3	$17.92	11.394%	$19.9618	$19.96	$19.95	$20.00
Purchase #4	$240.90	3.722%	$249.8663	$249.87	$249.85	$249.90
Purchase #5	$36.43	9.428%	$39.8646	$39.86	$39.85	$39.90
Purchase #6	$92.56	8.740%	$100.6497	$100.65	$100.65	$100.60
Purchase #7	$135.98	9.273%	$148.5894	$148.59	$148.60	$148.60
7 purchase totals =	$817.54		$879.3591	$879.36	$879.35	$879.40