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	$45.59	10.609%	$50.4266	$50.43	$50.45	$50.40
Purchase #2	$222.72	13.872%	$253.6157	$253.62	$253.60	$253.60
Purchase #3	$35.81	4.214%	$37.319	$37.32	$37.30	$37.30
Purchase #4	$198.85	8.297%	$215.3486	$215.35	$215.35	$215.30
Purchase #5	$152.48	9.500%	$166.9656	$166.97	$166.95	$167.00
Purchase #6	$139.72	5.302%	$147.128	$147.13	$147.15	$147.10
Purchase #7	$222.82	4.741%	$233.3839	$233.38	$233.40	$233.40
7 purchase totals =	$1,017.99		$1,104.1874	$1,104.20	$1,104.20	$1,104.10