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	$171.72	10.842%	$190.3379	$190.34	$190.35	$190.30
Purchase #2	$164.62	13.611%	$187.0264	$187.03	$187.05	$187.00
Purchase #3	$75.71	7.759%	$81.5843	$81.58	$81.60	$81.60
Purchase #4	$218.76	7.774%	$235.7664	$235.77	$235.75	$235.80
Purchase #5	$138.69	9.761%	$152.2275	$152.23	$152.25	$152.20
Purchase #6	$200.70	11.714%	$224.21	$224.21	$224.20	$224.20
Purchase #7	$215.26	6.567%	$229.3961	$229.40	$229.40	$229.40
7 purchase totals =	$1,185.46		$1,300.5486	$1,300.56	$1,300.60	$1,300.50