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	$119.74	12.238%	$134.3938	$134.39	$134.40	$134.40
Purchase #2	$19.81	5.589%	$20.9172	$20.92	$20.90	$20.90
Purchase #3	$82.49	4.135%	$85.901	$85.90	$85.90	$85.90
Purchase #4	$54.48	5.400%	$57.4219	$57.42	$57.40	$57.40
Purchase #5	$131.74	10.502%	$145.5753	$145.58	$145.60	$145.60
Purchase #6	$108.76	3.366%	$112.4209	$112.42	$112.40	$112.40
Purchase #7	$207.59	13.617%	$235.8575	$235.86	$235.85	$235.90
7 purchase totals =	$724.61		$792.4876	$792.49	$792.45	$792.50