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	$90.95	5.566%	$96.0123	$96.01	$96.00	$96.00
Purchase #2	$124.39	6.687%	$132.708	$132.71	$132.70	$132.70
Purchase #3	$158.75	5.148%	$166.9225	$166.92	$166.90	$166.90
Purchase #4	$215.60	5.360%	$227.1562	$227.16	$227.15	$227.20
Purchase #5	$250.52	10.735%	$277.4133	$277.41	$277.40	$277.40
Purchase #6	$33.44	11.511%	$37.2893	$37.29	$37.30	$37.30
Purchase #7	$171.27	8.352%	$185.5745	$185.57	$185.55	$185.60
7 purchase totals =	$1,044.92		$1,123.0761	$1,123.07	$1,123.00	$1,123.10