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	$173.90	10.259%	$191.7404	$191.74	$191.75	$191.70
Purchase #2	$83.48	5.704%	$88.2417	$88.24	$88.25	$88.20
Purchase #3	$72.98	6.259%	$77.5478	$77.55	$77.55	$77.50
Purchase #4	$18.47	6.795%	$19.725	$19.73	$19.75	$19.70
Purchase #5	$126.64	11.521%	$141.2302	$141.23	$141.25	$141.20
Purchase #6	$37.64	4.480%	$39.3263	$39.33	$39.35	$39.30
Purchase #7	$147.50	13.477%	$167.3786	$167.38	$167.40	$167.40
7 purchase totals =	$660.61		$725.1900	$725.20	$725.30	$725.00