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	$134.51	7.635%	$144.7798	$144.78	$144.80	$144.80
Purchase #2	$125.66	6.117%	$133.3466	$133.35	$133.35	$133.30
Purchase #3	$168.62	3.790%	$175.0107	$175.01	$175.00	$175.00
Purchase #4	$40.88	6.343%	$43.473	$43.47	$43.45	$43.50
Purchase #5	$52.96	4.520%	$55.3538	$55.35	$55.35	$55.40
Purchase #6	$245.64	7.578%	$264.2546	$264.25	$264.25	$264.30
Purchase #7	$33.58	10.872%	$37.2308	$37.23	$37.25	$37.20
7 purchase totals =	$801.85		$853.4493	$853.44	$853.45	$853.50