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	$173.62	9.727%	$190.508	$190.51	$190.50	$190.50
Purchase #2	$156.89	11.702%	$175.2493	$175.25	$175.25	$175.20
Purchase #3	$98.81	4.764%	$103.5173	$103.52	$103.50	$103.50
Purchase #4	$129.39	5.440%	$136.4288	$136.43	$136.45	$136.40
Purchase #5	$174.53	9.565%	$191.2238	$191.22	$191.20	$191.20
Purchase #6	$179.42	7.496%	$192.8693	$192.87	$192.85	$192.90
Purchase #7	$113.56	11.644%	$126.7829	$126.78	$126.80	$126.80
7 purchase totals =	$1,026.22		$1,116.5794	$1,116.58	$1,116.55	$1,116.50