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	$93.96	13.713%	$106.8447	$106.84	$106.85	$106.80
Purchase #2	$222.48	11.395%	$247.8316	$247.83	$247.85	$247.80
Purchase #3	$195.96	4.734%	$205.2367	$205.24	$205.25	$205.20
Purchase #4	$208.75	4.348%	$217.8265	$217.83	$217.85	$217.80
Purchase #5	$106.85	4.518%	$111.6775	$111.68	$111.70	$111.70
Purchase #6	$85.37	10.600%	$94.4192	$94.42	$94.40	$94.40
Purchase #7	$35.35	5.804%	$37.4017	$37.40	$37.40	$37.40
7 purchase totals =	$948.72		$1,021.2379	$1,021.24	$1,021.30	$1,021.10