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	$201.53	6.725%	$215.0829	$215.08	$215.10	$215.10
Purchase #2	$150.39	13.837%	$171.1995	$171.20	$171.20	$171.20
Purchase #3	$34.32	8.756%	$37.3251	$37.33	$37.35	$37.30
Purchase #4	$153.29	8.734%	$166.6783	$166.68	$166.70	$166.70
Purchase #5	$130.56	8.223%	$141.2959	$141.30	$141.30	$141.30
Purchase #6	$75.45	4.555%	$78.8867	$78.89	$78.90	$78.90
Purchase #7	$16.92	12.524%	$19.0391	$19.04	$19.05	$19.00
7 purchase totals =	$762.46		$829.5075	$829.52	$829.60	$829.50