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	$185.47	4.856%	$194.4764	$194.48	$194.50	$194.50
Purchase #2	$89.27	11.646%	$99.6664	$99.67	$99.65	$99.70
Purchase #3	$132.54	12.132%	$148.6198	$148.62	$148.60	$148.60
Purchase #4	$111.55	5.626%	$117.8258	$117.83	$117.85	$117.80
Purchase #5	$209.93	5.820%	$222.1479	$222.15	$222.15	$222.10
Purchase #6	$170.97	6.367%	$181.8557	$181.86	$181.85	$181.90
Purchase #7	$148.46	5.160%	$156.1205	$156.12	$156.10	$156.10
7 purchase totals =	$1,048.19		$1,120.7125	$1,120.73	$1,120.70	$1,120.70