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	$207.40	9.656%	$227.4265	$227.43	$227.45	$227.40
Purchase #2	$75.72	12.475%	$85.1661	$85.17	$85.15	$85.20
Purchase #3	$81.61	9.798%	$89.6061	$89.61	$89.60	$89.60
Purchase #4	$192.86	4.553%	$201.6409	$201.64	$201.65	$201.60
Purchase #5	$135.52	3.449%	$140.1941	$140.19	$140.20	$140.20
Purchase #6	$56.41	8.838%	$61.3955	$61.40	$61.40	$61.40
Purchase #7	$88.72	11.772%	$99.1641	$99.16	$99.15	$99.20
7 purchase totals =	$838.24		$904.5933	$904.60	$904.60	$904.60