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	$211.41	8.503%	$229.3862	$229.39	$229.40	$229.40
Purchase #2	$248.45	5.757%	$262.7533	$262.75	$262.75	$262.80
Purchase #3	$123.64	8.273%	$133.8687	$133.87	$133.85	$133.90
Purchase #4	$176.61	12.446%	$198.5909	$198.59	$198.60	$198.60
Purchase #5	$45.30	9.147%	$49.4436	$49.44	$49.45	$49.40
Purchase #6	$55.62	7.182%	$59.6146	$59.61	$59.60	$59.60
Purchase #7	$135.44	8.333%	$146.7262	$146.73	$146.75	$146.70
7 purchase totals =	$996.47		$1,080.3835	$1,080.38	$1,080.40	$1,080.40