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	$196.30	13.642%	$223.0792	$223.08	$223.10	$223.10
Purchase #2	$40.74	6.836%	$43.525	$43.53	$43.55	$43.50
Purchase #3	$14.82	9.505%	$16.2286	$16.23	$16.25	$16.20
Purchase #4	$205.34	8.412%	$222.6132	$222.61	$222.60	$222.60
Purchase #5	$143.79	5.196%	$151.2613	$151.26	$151.25	$151.30
Purchase #6	$180.26	4.111%	$187.6705	$187.67	$187.65	$187.70
Purchase #7	$121.66	13.370%	$137.9259	$137.93	$137.95	$137.90
7 purchase totals =	$902.91		$982.3037	$982.31	$982.35	$982.30