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	$182.89	4.388%	$190.9152	$190.92	$190.90	$190.90
Purchase #2	$152.27	4.788%	$159.5607	$159.56	$159.55	$159.60
Purchase #3	$80.95	6.678%	$86.3558	$86.36	$86.35	$86.40
Purchase #4	$28.35	10.716%	$31.388	$31.39	$31.40	$31.40
Purchase #5	$126.92	8.653%	$137.9024	$137.90	$137.90	$137.90
Purchase #6	$98.43	11.674%	$109.9207	$109.92	$109.90	$109.90
Purchase #7	$151.82	7.407%	$163.0653	$163.07	$163.05	$163.10
7 purchase totals =	$821.63		$879.1081	$879.12	$879.05	$879.20