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	$210.54	4.479%	$219.9701	$219.97	$219.95	$220.00
Purchase #2	$42.81	7.870%	$46.1791	$46.18	$46.20	$46.20
Purchase #3	$142.89	5.355%	$150.5418	$150.54	$150.55	$150.50
Purchase #4	$246.72	10.396%	$272.369	$272.37	$272.35	$272.40
Purchase #5	$140.85	12.611%	$158.6126	$158.61	$158.60	$158.60
Purchase #6	$82.82	13.531%	$94.0264	$94.03	$94.05	$94.00
Purchase #7	$150.56	9.194%	$164.4025	$164.40	$164.40	$164.40
7 purchase totals =	$1,017.19		$1,106.1015	$1,106.10	$1,106.10	$1,106.10