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	$205.72	7.214%	$220.5606	$220.56	$220.55	$220.60
Purchase #2	$184.44	6.412%	$196.2663	$196.27	$196.25	$196.30
Purchase #3	$6.40	10.296%	$7.0589	$7.06	$7.05	$7.10
Purchase #4	$110.92	12.594%	$124.8893	$124.89	$124.90	$124.90
Purchase #5	$158.43	5.649%	$167.3797	$167.38	$167.40	$167.40
Purchase #6	$213.60	9.369%	$233.6122	$233.61	$233.60	$233.60
Purchase #7	$197.89	3.697%	$205.206	$205.21	$205.20	$205.20
7 purchase totals =	$1,077.40		$1,154.9730	$1,154.98	$1,154.95	$1,155.10