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	$37.67	10.733%	$41.7131	$41.71	$41.70	$41.70
Purchase #2	$222.87	6.788%	$237.9984	$238.00	$238.00	$238.00
Purchase #3	$183.54	3.153%	$189.327	$189.33	$189.35	$189.30
Purchase #4	$48.98	9.330%	$53.5498	$53.55	$53.55	$53.50
Purchase #5	$169.35	8.227%	$183.2824	$183.28	$183.30	$183.30
Purchase #6	$135.81	9.210%	$148.3181	$148.32	$148.30	$148.30
Purchase #7	$151.25	7.302%	$162.2943	$162.29	$162.30	$162.30
7 purchase totals =	$949.47		$1,016.4831	$1,016.48	$1,016.50	$1,016.40