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	$96.73	8.846%	$105.2867	$105.29	$105.30	$105.30
Purchase #2	$17.37	7.504%	$18.6734	$18.67	$18.65	$18.70
Purchase #3	$247.36	13.795%	$281.4833	$281.48	$281.50	$281.50
Purchase #4	$164.56	6.102%	$174.6015	$174.60	$174.60	$174.60
Purchase #5	$152.26	10.553%	$168.328	$168.33	$168.35	$168.30
Purchase #6	$95.57	10.632%	$105.731	$105.73	$105.75	$105.70
Purchase #7	$182.40	10.141%	$200.8972	$200.90	$200.90	$200.90
7 purchase totals =	$956.25		$1,055.0011	$1,055.00	$1,055.05	$1,055.00