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	$40.58	13.572%	$46.0875	$46.09	$46.10	$46.10
Purchase #2	$199.52	8.641%	$216.7605	$216.76	$216.75	$216.80
Purchase #3	$163.96	13.109%	$185.4535	$185.45	$185.45	$185.50
Purchase #4	$37.49	12.141%	$42.0417	$42.04	$42.05	$42.00
Purchase #5	$72.68	13.614%	$82.5747	$82.57	$82.55	$82.60
Purchase #6	$39.79	10.261%	$43.8729	$43.87	$43.85	$43.90
Purchase #7	$93.31	3.252%	$96.3444	$96.34	$96.35	$96.30
7 purchase totals =	$647.33		$713.1352	$713.12	$713.10	$713.20