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	$231.27	4.163%	$240.8978	$240.90	$240.90	$240.90
Purchase #2	$17.82	9.348%	$19.4858	$19.49	$19.50	$19.50
Purchase #3	$51.65	6.562%	$55.0393	$55.04	$55.05	$55.00
Purchase #4	$54.57	4.263%	$56.8963	$56.90	$56.90	$56.90
Purchase #5	$21.74	12.584%	$24.4758	$24.48	$24.50	$24.50
Purchase #6	$154.97	3.174%	$159.8887	$159.89	$159.90	$159.90
Purchase #7	$125.96	13.414%	$142.8563	$142.86	$142.85	$142.90
7 purchase totals =	$657.98		$699.5400	$699.56	$699.60	$699.60