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	$233.25	6.478%	$248.3599	$248.36	$248.35	$248.40
Purchase #2	$22.81	5.754%	$24.1225	$24.12	$24.10	$24.10
Purchase #3	$51.95	13.754%	$59.0952	$59.10	$59.10	$59.10
Purchase #4	$174.96	11.168%	$194.4995	$194.50	$194.50	$194.50
Purchase #5	$241.40	4.853%	$253.1151	$253.12	$253.10	$253.10
Purchase #6	$139.73	8.805%	$152.0332	$152.03	$152.05	$152.00
Purchase #7	$122.61	13.758%	$139.4787	$139.48	$139.50	$139.50
7 purchase totals =	$986.71		$1,070.7041	$1,070.71	$1,070.70	$1,070.70