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	$69.85	11.616%	$77.9638	$77.96	$77.95	$78.00
Purchase #2	$110.92	12.248%	$124.5055	$124.51	$124.50	$124.50
Purchase #3	$13.63	7.768%	$14.6888	$14.69	$14.70	$14.70
Purchase #4	$59.79	4.428%	$62.4375	$62.44	$62.45	$62.40
Purchase #5	$92.47	6.399%	$98.3872	$98.39	$98.40	$98.40
Purchase #6	$90.55	10.280%	$99.8585	$99.86	$99.85	$99.90
Purchase #7	$92.76	12.756%	$104.5925	$104.59	$104.60	$104.60
7 purchase totals =	$529.97		$582.4338	$582.44	$582.45	$582.50