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	$134.79	13.477%	$152.9556	$152.96	$152.95	$153.00
Purchase #2	$147.96	5.639%	$156.3035	$156.30	$156.30	$156.30
Purchase #3	$52.79	9.852%	$57.9909	$57.99	$58.00	$58.00
Purchase #4	$13.69	13.435%	$15.5293	$15.53	$15.55	$15.50
Purchase #5	$30.91	8.370%	$33.4972	$33.50	$33.50	$33.50
Purchase #6	$11.41	4.417%	$11.914	$11.91	$11.90	$11.90
Purchase #7	$231.87	3.265%	$239.4406	$239.44	$239.45	$239.40
7 purchase totals =	$623.42		$667.6311	$667.63	$667.65	$667.60