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	$218.61	12.261%	$245.4138	$245.41	$245.40	$245.40
Purchase #2	$155.33	12.329%	$174.4806	$174.48	$174.50	$174.50
Purchase #3	$139.82	4.790%	$146.5174	$146.52	$146.50	$146.50
Purchase #4	$39.54	12.476%	$44.473	$44.47	$44.45	$44.50
Purchase #5	$109.31	4.271%	$113.9786	$113.98	$114.00	$114.00
Purchase #6	$199.47	10.619%	$220.6517	$220.65	$220.65	$220.70
Purchase #7	$119.96	9.772%	$131.6825	$131.68	$131.70	$131.70
7 purchase totals =	$982.04		$1,077.1976	$1,077.19	$1,077.20	$1,077.30