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	$99.72	4.389%	$104.0967	$104.10	$104.10	$104.10
Purchase #2	$219.50	11.357%	$244.4286	$244.43	$244.45	$244.40
Purchase #3	$73.85	11.648%	$82.452	$82.45	$82.45	$82.50
Purchase #4	$245.60	10.294%	$270.8821	$270.88	$270.90	$270.90
Purchase #5	$184.74	5.266%	$194.4684	$194.47	$194.45	$194.50
Purchase #6	$111.60	13.430%	$126.5879	$126.59	$126.60	$126.60
Purchase #7	$62.89	7.323%	$67.4954	$67.50	$67.50	$67.50
7 purchase totals =	$997.90		$1,090.4111	$1,090.42	$1,090.45	$1,090.50