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	$99.62	13.232%	$112.8017	$112.80	$112.80	$112.80
Purchase #2	$102.32	13.704%	$116.3419	$116.34	$116.35	$116.30
Purchase #3	$68.70	3.799%	$71.3099	$71.31	$71.30	$71.30
Purchase #4	$86.26	6.195%	$91.6038	$91.60	$91.60	$91.60
Purchase #5	$152.28	12.302%	$171.0135	$171.01	$171.00	$171.00
Purchase #6	$236.58	7.856%	$255.1657	$255.17	$255.15	$255.20
Purchase #7	$105.54	3.487%	$109.2202	$109.22	$109.20	$109.20
7 purchase totals =	$851.30		$927.4567	$927.45	$927.40	$927.40