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	$94.85	5.140%	$99.7253	$99.73	$99.75	$99.70
Purchase #2	$228.96	13.361%	$259.5513	$259.55	$259.55	$259.60
Purchase #3	$33.47	4.493%	$34.9738	$34.97	$34.95	$35.00
Purchase #4	$120.30	13.626%	$136.6921	$136.69	$136.70	$136.70
Purchase #5	$213.82	12.406%	$240.3465	$240.35	$240.35	$240.30
Purchase #6	$175.81	13.844%	$200.1491	$200.15	$200.15	$200.10
Purchase #7	$99.50	10.216%	$109.6649	$109.66	$109.65	$109.70
7 purchase totals =	$966.71		$1,081.1030	$1,081.10	$1,081.10	$1,081.10