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	$228.89	10.644%	$253.2531	$253.25	$253.25	$253.30
Purchase #2	$48.61	9.450%	$53.2036	$53.20	$53.20	$53.20
Purchase #3	$248.58	6.782%	$265.4387	$265.44	$265.45	$265.40
Purchase #4	$224.85	10.658%	$248.8145	$248.81	$248.80	$248.80
Purchase #5	$73.87	6.206%	$78.4544	$78.45	$78.45	$78.50
Purchase #6	$152.53	11.178%	$169.5798	$169.58	$169.60	$169.60
Purchase #7	$37.30	5.175%	$39.2303	$39.23	$39.25	$39.20
7 purchase totals =	$1,014.63		$1,107.9744	$1,107.96	$1,108.00	$1,108.00