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	$50.94	6.585%	$54.2944	$54.29	$54.30	$54.30
Purchase #2	$167.92	10.211%	$185.0663	$185.07	$185.05	$185.10
Purchase #3	$57.57	11.699%	$64.3051	$64.31	$64.30	$64.30
Purchase #4	$221.98	8.384%	$240.5908	$240.59	$240.60	$240.60
Purchase #5	$53.89	3.272%	$55.6533	$55.65	$55.65	$55.70
Purchase #6	$57.87	11.693%	$64.6367	$64.64	$64.65	$64.60
Purchase #7	$155.70	8.347%	$168.6963	$168.70	$168.70	$168.70
7 purchase totals =	$765.87		$833.2429	$833.25	$833.25	$833.30