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	$184.48	5.314%	$194.2833	$194.28	$194.30	$194.30
Purchase #2	$224.54	6.450%	$239.0228	$239.02	$239.00	$239.00
Purchase #3	$217.86	7.344%	$233.8596	$233.86	$233.85	$233.90
Purchase #4	$83.89	8.185%	$90.7564	$90.76	$90.75	$90.80
Purchase #5	$208.59	6.319%	$221.7708	$221.77	$221.75	$221.80
Purchase #6	$8.43	3.863%	$8.7557	$8.76	$8.75	$8.80
Purchase #7	$183.83	13.361%	$208.3915	$208.39	$208.40	$208.40
7 purchase totals =	$1,111.62		$1,196.8401	$1,196.84	$1,196.80	$1,197.00