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	$48.53	13.771%	$55.2131	$55.21	$55.20	$55.20
Purchase #2	$76.77	11.659%	$85.7206	$85.72	$85.70	$85.70
Purchase #3	$192.59	4.331%	$200.9311	$200.93	$200.95	$200.90
Purchase #4	$181.59	10.542%	$200.7332	$200.73	$200.75	$200.70
Purchase #5	$190.83	9.117%	$208.228	$208.23	$208.25	$208.20
Purchase #6	$227.60	5.474%	$240.0588	$240.06	$240.05	$240.10
Purchase #7	$64.92	7.688%	$69.911	$69.91	$69.90	$69.90
7 purchase totals =	$982.83		$1,060.7958	$1,060.79	$1,060.80	$1,060.70