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	$12.76	13.436%	$14.4744	$14.47	$14.45	$14.50
Purchase #2	$131.71	7.796%	$141.9781	$141.98	$142.00	$142.00
Purchase #3	$130.76	8.810%	$142.28	$142.28	$142.30	$142.30
Purchase #4	$78.47	10.470%	$86.6858	$86.69	$86.70	$86.70
Purchase #5	$159.82	12.302%	$179.4811	$179.48	$179.50	$179.50
Purchase #6	$144.80	9.346%	$158.333	$158.33	$158.35	$158.30
Purchase #7	$242.85	12.459%	$273.1067	$273.11	$273.10	$273.10
7 purchase totals =	$901.17		$996.3391	$996.34	$996.40	$996.40