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	$136.41	11.572%	$152.1954	$152.20	$152.20	$152.20
Purchase #2	$33.76	10.728%	$37.3818	$37.38	$37.40	$37.40
Purchase #3	$69.45	4.343%	$72.4662	$72.47	$72.45	$72.50
Purchase #4	$152.72	11.320%	$170.0079	$170.01	$170.00	$170.00
Purchase #5	$228.72	8.623%	$248.4425	$248.44	$248.45	$248.40
Purchase #6	$196.40	4.418%	$205.077	$205.08	$205.10	$205.10
Purchase #7	$105.43	13.443%	$119.603	$119.60	$119.60	$119.60
7 purchase totals =	$922.89		$1,005.1738	$1,005.18	$1,005.20	$1,005.20