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	$171.45	4.553%	$179.2561	$179.26	$179.25	$179.30
Purchase #2	$57.65	3.709%	$59.7882	$59.79	$59.80	$59.80
Purchase #3	$208.35	4.211%	$217.1236	$217.12	$217.10	$217.10
Purchase #4	$64.33	11.456%	$71.6996	$71.70	$71.70	$71.70
Purchase #5	$249.63	13.549%	$283.4524	$283.45	$283.45	$283.50
Purchase #6	$104.49	3.601%	$108.2527	$108.25	$108.25	$108.30
Purchase #7	$107.59	3.515%	$111.3718	$111.37	$111.35	$111.40
7 purchase totals =	$963.49		$1,030.9444	$1,030.94	$1,030.90	$1,031.10