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	$82.46	4.118%	$85.8557	$85.86	$85.85	$85.90
Purchase #2	$201.59	11.842%	$225.4623	$225.46	$225.45	$225.50
Purchase #3	$80.39	13.446%	$91.1992	$91.20	$91.20	$91.20
Purchase #4	$135.36	5.353%	$142.6058	$142.61	$142.60	$142.60
Purchase #5	$85.48	6.305%	$90.8695	$90.87	$90.85	$90.90
Purchase #6	$150.29	9.417%	$164.4428	$164.44	$164.45	$164.40
Purchase #7	$226.67	3.662%	$234.9707	$234.97	$234.95	$235.00
7 purchase totals =	$962.24		$1,035.4060	$1,035.41	$1,035.35	$1,035.50