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	$141.25	8.456%	$153.1941	$153.19	$153.20	$153.20
Purchase #2	$62.89	13.389%	$71.3103	$71.31	$71.30	$71.30
Purchase #3	$69.33	5.109%	$72.8721	$72.87	$72.85	$72.90
Purchase #4	$25.69	8.564%	$27.8901	$27.89	$27.90	$27.90
Purchase #5	$69.25	6.659%	$73.8614	$73.86	$73.85	$73.90
Purchase #6	$34.52	9.345%	$37.7459	$37.75	$37.75	$37.70
Purchase #7	$95.51	8.561%	$103.6866	$103.69	$103.70	$103.70
7 purchase totals =	$498.44		$540.5605	$540.56	$540.55	$540.60