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	$222.70	11.109%	$247.4397	$247.44	$247.45	$247.40
Purchase #2	$200.35	9.783%	$219.9502	$219.95	$219.95	$220.00
Purchase #3	$71.85	9.375%	$78.5859	$78.59	$78.60	$78.60
Purchase #4	$203.34	9.441%	$222.5373	$222.54	$222.55	$222.50
Purchase #5	$78.70	8.398%	$85.3092	$85.31	$85.30	$85.30
Purchase #6	$248.26	3.515%	$256.9863	$256.99	$257.00	$257.00
Purchase #7	$193.28	7.868%	$208.4873	$208.49	$208.50	$208.50
7 purchase totals =	$1,218.48		$1,319.2959	$1,319.31	$1,319.35	$1,319.30