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	$78.63	12.680%	$88.6003	$88.60	$88.60	$88.60
Purchase #2	$57.84	4.564%	$60.4798	$60.48	$60.50	$60.50
Purchase #3	$38.34	13.141%	$43.3783	$43.38	$43.40	$43.40
Purchase #4	$244.85	3.536%	$253.5079	$253.51	$253.50	$253.50
Purchase #5	$227.28	8.543%	$246.6965	$246.70	$246.70	$246.70
Purchase #6	$98.84	7.314%	$106.0692	$106.07	$106.05	$106.10
Purchase #7	$196.71	13.631%	$223.5235	$223.52	$223.50	$223.50
7 purchase totals =	$942.49		$1,022.2555	$1,022.26	$1,022.25	$1,022.30