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	$20.38	7.331%	$21.8741	$21.87	$21.85	$21.90
Purchase #2	$141.39	7.342%	$151.7709	$151.77	$151.75	$151.80
Purchase #3	$207.51	10.555%	$229.4127	$229.41	$229.40	$229.40
Purchase #4	$99.29	11.465%	$110.6736	$110.67	$110.65	$110.70
Purchase #5	$34.58	8.280%	$37.4432	$37.44	$37.45	$37.40
Purchase #6	$247.85	13.348%	$280.933	$280.93	$280.95	$280.90
Purchase #7	$205.67	8.159%	$222.4506	$222.45	$222.45	$222.50
7 purchase totals =	$956.67		$1,054.5581	$1,054.54	$1,054.50	$1,054.60