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	$196.25	13.372%	$222.4926	$222.49	$222.50	$222.50
Purchase #2	$105.87	12.216%	$118.8031	$118.80	$118.80	$118.80
Purchase #3	$150.95	13.532%	$171.3766	$171.38	$171.40	$171.40
Purchase #4	$53.48	10.349%	$59.0146	$59.01	$59.00	$59.00
Purchase #5	$98.50	8.347%	$106.7218	$106.72	$106.70	$106.70
Purchase #6	$248.90	5.461%	$262.4924	$262.49	$262.50	$262.50
Purchase #7	$133.91	8.134%	$144.8022	$144.80	$144.80	$144.80
7 purchase totals =	$987.86		$1,085.7033	$1,085.69	$1,085.70	$1,085.70