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	$82.35	10.481%	$90.9811	$90.98	$91.00	$91.00
Purchase #2	$236.33	8.561%	$256.5622	$256.56	$256.55	$256.60
Purchase #3	$199.29	9.825%	$218.8702	$218.87	$218.85	$218.90
Purchase #4	$32.91	10.668%	$36.4208	$36.42	$36.40	$36.40
Purchase #5	$155.54	11.431%	$173.3198	$173.32	$173.30	$173.30
Purchase #6	$106.84	10.764%	$118.3403	$118.34	$118.35	$118.30
Purchase #7	$107.55	13.107%	$121.6466	$121.65	$121.65	$121.60
7 purchase totals =	$920.81		$1,016.1410	$1,016.14	$1,016.10	$1,016.10