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	$205.70	13.716%	$233.9138	$233.91	$233.90	$233.90
Purchase #2	$147.40	10.293%	$162.5719	$162.57	$162.55	$162.60
Purchase #3	$213.62	11.858%	$238.9511	$238.95	$238.95	$239.00
Purchase #4	$58.34	5.602%	$61.6082	$61.61	$61.60	$61.60
Purchase #5	$18.99	9.206%	$20.7382	$20.74	$20.75	$20.70
Purchase #6	$218.89	11.407%	$243.8588	$243.86	$243.85	$243.90
Purchase #7	$198.31	6.838%	$211.8704	$211.87	$211.85	$211.90
7 purchase totals =	$1,061.25		$1,173.5124	$1,173.51	$1,173.45	$1,173.60