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	$198.47	8.174%	$214.6929	$214.69	$214.70	$214.70
Purchase #2	$227.53	12.699%	$256.424	$256.42	$256.40	$256.40
Purchase #3	$162.45	9.488%	$177.8633	$177.86	$177.85	$177.90
Purchase #4	$96.86	4.728%	$101.4395	$101.44	$101.45	$101.40
Purchase #5	$57.52	13.525%	$65.2996	$65.30	$65.30	$65.30
Purchase #6	$12.31	11.503%	$13.726	$13.73	$13.75	$13.70
Purchase #7	$246.58	9.725%	$270.5599	$270.56	$270.55	$270.60
7 purchase totals =	$1,001.72		$1,100.0052	$1,100.00	$1,100.00	$1,100.00