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	$96.79	5.347%	$101.9654	$101.97	$101.95	$102.00
Purchase #2	$209.94	7.587%	$225.8681	$225.87	$225.85	$225.90
Purchase #3	$91.34	11.583%	$101.9199	$101.92	$101.90	$101.90
Purchase #4	$206.40	13.798%	$234.8791	$234.88	$234.90	$234.90
Purchase #5	$172.82	6.733%	$184.456	$184.46	$184.45	$184.50
Purchase #6	$106.31	9.827%	$116.7571	$116.76	$116.75	$116.80
Purchase #7	$174.95	12.482%	$196.7873	$196.79	$196.80	$196.80
7 purchase totals =	$1,058.55		$1,162.6329	$1,162.65	$1,162.60	$1,162.80