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	$164.52	9.599%	$180.3123	$180.31	$180.30	$180.30
Purchase #2	$214.39	12.332%	$240.8286	$240.83	$240.85	$240.80
Purchase #3	$57.58	8.344%	$62.3845	$62.38	$62.40	$62.40
Purchase #4	$183.73	4.357%	$191.7351	$191.74	$191.75	$191.70
Purchase #5	$224.39	4.252%	$233.9311	$233.93	$233.95	$233.90
Purchase #6	$73.37	4.558%	$76.7142	$76.71	$76.70	$76.70
Purchase #7	$93.52	6.219%	$99.336	$99.34	$99.35	$99.30
7 purchase totals =	$1,011.50		$1,085.2418	$1,085.24	$1,085.30	$1,085.10