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	$81.35	4.859%	$85.3028	$85.30	$85.30	$85.30
Purchase #2	$14.81	4.285%	$15.4446	$15.44	$15.45	$15.40
Purchase #3	$241.79	10.611%	$267.4463	$267.45	$267.45	$267.40
Purchase #4	$30.31	6.691%	$32.338	$32.34	$32.35	$32.30
Purchase #5	$71.52	12.759%	$80.6452	$80.65	$80.65	$80.60
Purchase #6	$17.73	10.261%	$19.5493	$19.55	$19.55	$19.50
Purchase #7	$164.28	12.612%	$184.999	$185.00	$185.00	$185.00
7 purchase totals =	$621.79		$685.7252	$685.73	$685.75	$685.50