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	$99.37	7.617%	$106.939	$106.94	$106.95	$106.90
Purchase #2	$54.75	12.603%	$61.6501	$61.65	$61.65	$61.70
Purchase #3	$59.29	9.769%	$65.082	$65.08	$65.10	$65.10
Purchase #4	$218.35	10.323%	$240.8903	$240.89	$240.90	$240.90
Purchase #5	$180.96	9.231%	$197.6644	$197.66	$197.65	$197.70
Purchase #6	$153.85	9.588%	$168.6011	$168.60	$168.60	$168.60
Purchase #7	$39.86	6.348%	$42.3903	$42.39	$42.40	$42.40
7 purchase totals =	$806.43		$883.2172	$883.21	$883.25	$883.30