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	$205.27	5.597%	$216.759	$216.76	$216.75	$216.80
Purchase #2	$52.71	12.123%	$59.1	$59.10	$59.10	$59.10
Purchase #3	$169.56	10.762%	$187.808	$187.81	$187.80	$187.80
Purchase #4	$82.84	9.847%	$90.9973	$91.00	$91.00	$91.00
Purchase #5	$115.83	12.870%	$130.7373	$130.74	$130.75	$130.70
Purchase #6	$18.50	11.866%	$20.6952	$20.70	$20.70	$20.70
Purchase #7	$154.47	8.424%	$167.4826	$167.48	$167.50	$167.50
7 purchase totals =	$799.18		$873.5794	$873.59	$873.60	$873.60