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	$160.38	7.665%	$172.6731	$172.67	$172.65	$172.70
Purchase #2	$249.69	5.284%	$262.8836	$262.88	$262.90	$262.90
Purchase #3	$168.65	12.528%	$189.7785	$189.78	$189.80	$189.80
Purchase #4	$59.69	9.242%	$65.2065	$65.21	$65.20	$65.20
Purchase #5	$83.54	13.212%	$94.5773	$94.58	$94.60	$94.60
Purchase #6	$177.31	9.750%	$194.5977	$194.60	$194.60	$194.60
Purchase #7	$98.28	13.787%	$111.8299	$111.83	$111.85	$111.80
7 purchase totals =	$997.54		$1,091.5466	$1,091.55	$1,091.60	$1,091.60