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	$246.62	4.215%	$257.015	$257.02	$257.00	$257.00
Purchase #2	$171.60	7.573%	$184.5953	$184.60	$184.60	$184.60
Purchase #3	$209.38	3.200%	$216.0802	$216.08	$216.10	$216.10
Purchase #4	$95.34	9.485%	$104.383	$104.38	$104.40	$104.40
Purchase #5	$141.95	7.670%	$152.8376	$152.84	$152.85	$152.80
Purchase #6	$88.62	13.200%	$100.3178	$100.32	$100.30	$100.30
Purchase #7	$42.77	8.789%	$46.5291	$46.53	$46.55	$46.50
7 purchase totals =	$996.28		$1,061.7580	$1,061.77	$1,061.80	$1,061.70