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	$244.25	11.481%	$272.2923	$272.29	$272.30	$272.30
Purchase #2	$67.42	7.473%	$72.4583	$72.46	$72.45	$72.50
Purchase #3	$192.43	3.274%	$198.7302	$198.73	$198.75	$198.70
Purchase #4	$153.58	9.704%	$168.4834	$168.48	$168.50	$168.50
Purchase #5	$129.29	6.254%	$137.3758	$137.38	$137.40	$137.40
Purchase #6	$130.49	10.324%	$143.9618	$143.96	$143.95	$144.00
Purchase #7	$55.64	6.607%	$59.3161	$59.32	$59.30	$59.30
7 purchase totals =	$973.10		$1,052.6179	$1,052.62	$1,052.65	$1,052.70