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	$55.61	7.448%	$59.7518	$59.75	$59.75	$59.80
Purchase #2	$180.95	9.507%	$198.1529	$198.15	$198.15	$198.20
Purchase #3	$101.61	6.817%	$108.5368	$108.54	$108.55	$108.50
Purchase #4	$213.44	9.674%	$234.0882	$234.09	$234.10	$234.10
Purchase #5	$167.66	12.316%	$188.309	$188.31	$188.30	$188.30
Purchase #6	$127.94	11.825%	$143.0689	$143.07	$143.05	$143.10
Purchase #7	$113.89	8.660%	$123.7529	$123.75	$123.75	$123.80
7 purchase totals =	$961.10		$1,055.6605	$1,055.66	$1,055.65	$1,055.80