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	$193.28	10.371%	$213.3251	$213.33	$213.35	$213.30
Purchase #2	$93.98	9.361%	$102.7775	$102.78	$102.80	$102.80
Purchase #3	$30.32	10.784%	$33.5897	$33.59	$33.60	$33.60
Purchase #4	$185.71	7.487%	$199.6141	$199.61	$199.60	$199.60
Purchase #5	$71.91	8.677%	$78.1496	$78.15	$78.15	$78.10
Purchase #6	$115.60	11.527%	$128.9252	$128.93	$128.95	$128.90
Purchase #7	$35.90	13.513%	$40.7512	$40.75	$40.75	$40.80
7 purchase totals =	$726.70		$797.1324	$797.14	$797.20	$797.10