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	$102.68	10.461%	$113.4214	$113.42	$113.40	$113.40
Purchase #2	$185.96	7.395%	$199.7117	$199.71	$199.70	$199.70
Purchase #3	$148.58	5.577%	$156.8663	$156.87	$156.85	$156.90
Purchase #4	$88.57	5.521%	$93.4599	$93.46	$93.45	$93.50
Purchase #5	$210.82	13.278%	$238.8127	$238.81	$238.80	$238.80
Purchase #6	$85.25	3.538%	$88.2661	$88.27	$88.25	$88.30
Purchase #7	$144.87	13.413%	$164.3014	$164.30	$164.30	$164.30
7 purchase totals =	$966.73		$1,054.8395	$1,054.84	$1,054.75	$1,054.90