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	$62.67	12.495%	$70.5006	$70.50	$70.50	$70.50
Purchase #2	$156.53	4.804%	$164.0497	$164.05	$164.05	$164.00
Purchase #3	$223.67	13.254%	$253.3152	$253.32	$253.30	$253.30
Purchase #4	$198.99	4.765%	$208.4719	$208.47	$208.45	$208.50
Purchase #5	$13.91	3.741%	$14.4304	$14.43	$14.45	$14.40
Purchase #6	$160.80	6.800%	$171.7344	$171.73	$171.75	$171.70
Purchase #7	$236.84	10.845%	$262.5253	$262.53	$262.55	$262.50
7 purchase totals =	$1,053.41		$1,145.0275	$1,145.03	$1,145.05	$1,144.90