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	$186.76	7.483%	$200.7353	$200.74	$200.75	$200.70
Purchase #2	$52.98	4.503%	$55.3657	$55.37	$55.35	$55.40
Purchase #3	$143.50	11.832%	$160.4789	$160.48	$160.50	$160.50
Purchase #4	$74.25	9.873%	$81.5807	$81.58	$81.60	$81.60
Purchase #5	$18.35	4.445%	$19.1657	$19.17	$19.15	$19.20
Purchase #6	$146.73	3.686%	$152.1385	$152.14	$152.15	$152.10
Purchase #7	$74.93	13.871%	$85.3235	$85.32	$85.30	$85.30
7 purchase totals =	$697.50		$754.7883	$754.80	$754.80	$754.80