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	$166.46	10.765%	$184.3794	$184.38	$184.40	$184.40
Purchase #2	$135.26	4.476%	$141.3142	$141.31	$141.30	$141.30
Purchase #3	$123.78	5.264%	$130.2958	$130.30	$130.30	$130.30
Purchase #4	$200.81	6.216%	$213.2923	$213.29	$213.30	$213.30
Purchase #5	$105.70	5.800%	$111.8306	$111.83	$111.85	$111.80
Purchase #6	$59.32	6.440%	$63.1402	$63.14	$63.15	$63.10
Purchase #7	$97.87	13.562%	$111.1431	$111.14	$111.15	$111.10
7 purchase totals =	$889.20		$955.3956	$955.39	$955.45	$955.30