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	$158.72	5.861%	$168.0226	$168.02	$168.00	$168.00
Purchase #2	$166.43	7.113%	$178.2682	$178.27	$178.25	$178.30
Purchase #3	$211.81	7.571%	$227.8461	$227.85	$227.85	$227.80
Purchase #4	$185.87	10.181%	$204.7934	$204.79	$204.80	$204.80
Purchase #5	$213.28	13.516%	$242.1069	$242.11	$242.10	$242.10
Purchase #6	$9.57	13.559%	$10.8676	$10.87	$10.85	$10.90
Purchase #7	$93.39	6.470%	$99.4323	$99.43	$99.45	$99.40
7 purchase totals =	$1,039.07		$1,131.3371	$1,131.34	$1,131.30	$1,131.30