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	$15.28	13.530%	$17.3474	$17.35	$17.35	$17.30
Purchase #2	$40.85	3.567%	$42.3071	$42.31	$42.30	$42.30
Purchase #3	$67.91	12.706%	$76.5386	$76.54	$76.55	$76.50
Purchase #4	$214.25	13.762%	$243.7351	$243.74	$243.75	$243.70
Purchase #5	$168.76	13.629%	$191.7603	$191.76	$191.75	$191.80
Purchase #6	$214.54	8.322%	$232.394	$232.39	$232.40	$232.40
Purchase #7	$189.89	13.380%	$215.2973	$215.30	$215.30	$215.30
7 purchase totals =	$911.48		$1,019.3798	$1,019.39	$1,019.40	$1,019.30