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	$178.55	6.830%	$190.745	$190.75	$190.75	$190.70
Purchase #2	$118.69	11.725%	$132.6064	$132.61	$132.60	$132.60
Purchase #3	$81.74	9.124%	$89.198	$89.20	$89.20	$89.20
Purchase #4	$216.35	6.460%	$230.3262	$230.33	$230.35	$230.30
Purchase #5	$80.83	11.306%	$89.9686	$89.97	$89.95	$90.00
Purchase #6	$160.87	13.348%	$182.3429	$182.34	$182.35	$182.30
Purchase #7	$168.85	12.855%	$190.5557	$190.56	$190.55	$190.60
7 purchase totals =	$1,005.88		$1,105.7428	$1,105.76	$1,105.75	$1,105.70