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	$74.91	4.632%	$78.3798	$78.38	$78.40	$78.40
Purchase #2	$219.93	12.576%	$247.5884	$247.59	$247.60	$247.60
Purchase #3	$16.96	5.681%	$17.9235	$17.92	$17.90	$17.90
Purchase #4	$174.61	11.718%	$195.0708	$195.07	$195.05	$195.10
Purchase #5	$238.83	13.250%	$270.475	$270.48	$270.50	$270.50
Purchase #6	$42.65	11.188%	$47.4217	$47.42	$47.40	$47.40
Purchase #7	$142.86	6.139%	$151.6302	$151.63	$151.65	$151.60
7 purchase totals =	$910.75		$1,008.4894	$1,008.49	$1,008.50	$1,008.50