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	$206.87	4.539%	$216.2598	$216.26	$216.25	$216.30
Purchase #2	$196.82	13.377%	$223.1486	$223.15	$223.15	$223.10
Purchase #3	$72.61	13.629%	$82.506	$82.51	$82.50	$82.50
Purchase #4	$184.72	5.314%	$194.536	$194.54	$194.55	$194.50
Purchase #5	$75.38	9.418%	$82.4793	$82.48	$82.50	$82.50
Purchase #6	$129.82	12.639%	$146.2279	$146.23	$146.25	$146.20
Purchase #7	$241.69	13.771%	$274.9731	$274.97	$274.95	$275.00
7 purchase totals =	$1,107.91		$1,220.1307	$1,220.14	$1,220.15	$1,220.10