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	$57.33	3.783%	$59.4988	$59.50	$59.50	$59.50
Purchase #2	$27.54	10.203%	$30.3499	$30.35	$30.35	$30.30
Purchase #3	$155.82	12.621%	$175.486	$175.49	$175.50	$175.50
Purchase #4	$76.97	5.674%	$81.3373	$81.34	$81.35	$81.30
Purchase #5	$128.41	4.309%	$133.9432	$133.94	$133.95	$133.90
Purchase #6	$85.46	4.152%	$89.0083	$89.01	$89.00	$89.00
Purchase #7	$34.54	8.685%	$37.5398	$37.54	$37.55	$37.50
7 purchase totals =	$566.07		$607.1633	$607.17	$607.20	$607.00