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	$94.53	5.580%	$99.8048	$99.80	$99.80	$99.80
Purchase #2	$201.56	7.632%	$216.9431	$216.94	$216.95	$216.90
Purchase #3	$183.28	7.267%	$196.599	$196.60	$196.60	$196.60
Purchase #4	$11.79	7.393%	$12.6616	$12.66	$12.65	$12.70
Purchase #5	$131.89	13.767%	$150.0473	$150.05	$150.05	$150.00
Purchase #6	$113.66	12.836%	$128.2494	$128.25	$128.25	$128.20
Purchase #7	$201.60	7.796%	$217.3167	$217.32	$217.30	$217.30
7 purchase totals =	$938.31		$1,021.6219	$1,021.62	$1,021.60	$1,021.50