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	$72.46	13.677%	$82.3704	$82.37	$82.35	$82.40
Purchase #2	$170.32	10.761%	$188.6481	$188.65	$188.65	$188.60
Purchase #3	$73.82	4.823%	$77.3803	$77.38	$77.40	$77.40
Purchase #4	$178.58	8.562%	$193.87	$193.87	$193.85	$193.90
Purchase #5	$163.50	5.560%	$172.5906	$172.59	$172.60	$172.60
Purchase #6	$180.47	10.448%	$199.3255	$199.33	$199.35	$199.30
Purchase #7	$25.43	6.499%	$27.0827	$27.08	$27.10	$27.10
7 purchase totals =	$864.58		$941.2676	$941.27	$941.30	$941.30