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	$109.95	6.377%	$116.9615	$116.96	$116.95	$117.00
Purchase #2	$153.36	12.473%	$172.4886	$172.49	$172.50	$172.50
Purchase #3	$231.72	13.422%	$262.8215	$262.82	$262.80	$262.80
Purchase #4	$213.59	4.564%	$223.3382	$223.34	$223.35	$223.30
Purchase #5	$107.58	6.834%	$114.932	$114.93	$114.95	$114.90
Purchase #6	$115.96	12.383%	$130.3193	$130.32	$130.30	$130.30
Purchase #7	$212.70	4.551%	$222.38	$222.38	$222.40	$222.40
7 purchase totals =	$1,144.86		$1,243.2411	$1,243.24	$1,243.25	$1,243.20