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	$89.54	7.221%	$96.0057	$96.01	$96.00	$96.00
Purchase #2	$203.85	5.528%	$215.1188	$215.12	$215.10	$215.10
Purchase #3	$108.79	11.607%	$121.4173	$121.42	$121.40	$121.40
Purchase #4	$213.61	4.109%	$222.3872	$222.39	$222.40	$222.40
Purchase #5	$209.77	12.174%	$235.3074	$235.31	$235.30	$235.30
Purchase #6	$70.95	12.535%	$79.8436	$79.84	$79.85	$79.80
Purchase #7	$42.40	9.476%	$46.4178	$46.42	$46.40	$46.40
7 purchase totals =	$938.91		$1,016.4978	$1,016.51	$1,016.45	$1,016.40