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	$154.98	6.847%	$165.5915	$165.59	$165.60	$165.60
Purchase #2	$219.52	13.864%	$249.9543	$249.95	$249.95	$250.00
Purchase #3	$189.39	10.412%	$209.1093	$209.11	$209.10	$209.10
Purchase #4	$173.92	5.497%	$183.4804	$183.48	$183.50	$183.50
Purchase #5	$56.54	7.181%	$60.6001	$60.60	$60.60	$60.60
Purchase #6	$162.71	7.250%	$174.5065	$174.51	$174.50	$174.50
Purchase #7	$92.63	8.493%	$100.4971	$100.50	$100.50	$100.50
7 purchase totals =	$1,049.69		$1,143.7392	$1,143.74	$1,143.75	$1,143.80