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	$160.71	4.341%	$167.6864	$167.69	$167.70	$167.70
Purchase #2	$249.67	11.415%	$278.1698	$278.17	$278.15	$278.20
Purchase #3	$106.25	7.394%	$114.1061	$114.11	$114.10	$114.10
Purchase #4	$156.84	7.404%	$168.4524	$168.45	$168.45	$168.50
Purchase #5	$198.85	12.385%	$223.4776	$223.48	$223.50	$223.50
Purchase #6	$76.89	11.598%	$85.8077	$85.81	$85.80	$85.80
Purchase #7	$128.90	12.861%	$145.4778	$145.48	$145.50	$145.50
7 purchase totals =	$1,078.11		$1,183.1778	$1,183.19	$1,183.20	$1,183.30