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	$153.83	7.338%	$165.118	$165.12	$165.10	$165.10
Purchase #2	$183.28	8.473%	$198.8093	$198.81	$198.80	$198.80
Purchase #3	$232.77	12.582%	$262.0571	$262.06	$262.05	$262.10
Purchase #4	$194.98	13.364%	$221.0371	$221.04	$221.05	$221.00
Purchase #5	$67.95	6.373%	$72.2805	$72.28	$72.30	$72.30
Purchase #6	$137.95	7.268%	$147.9762	$147.98	$148.00	$148.00
Purchase #7	$16.67	11.600%	$18.6037	$18.60	$18.60	$18.60
7 purchase totals =	$987.43		$1,085.8819	$1,085.89	$1,085.90	$1,085.90