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	$69.36	13.846%	$78.9636	$78.96	$78.95	$79.00
Purchase #2	$184.66	3.280%	$190.7168	$190.72	$190.70	$190.70
Purchase #3	$196.40	13.550%	$223.0122	$223.01	$223.00	$223.00
Purchase #4	$132.96	6.716%	$141.8896	$141.89	$141.90	$141.90
Purchase #5	$184.75	4.415%	$192.9067	$192.91	$192.90	$192.90
Purchase #6	$207.75	6.266%	$220.7676	$220.77	$220.75	$220.80
Purchase #7	$46.40	4.165%	$48.3326	$48.33	$48.35	$48.30
7 purchase totals =	$1,022.28		$1,096.5891	$1,096.59	$1,096.55	$1,096.60