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	$79.28	12.224%	$88.9712	$88.97	$88.95	$89.00
Purchase #2	$92.63	13.210%	$104.8664	$104.87	$104.85	$104.90
Purchase #3	$33.62	12.828%	$37.9328	$37.93	$37.95	$37.90
Purchase #4	$32.89	9.244%	$35.9304	$35.93	$35.95	$35.90
Purchase #5	$155.76	8.247%	$168.6055	$168.61	$168.60	$168.60
Purchase #6	$148.90	5.161%	$156.5847	$156.58	$156.60	$156.60
Purchase #7	$82.88	13.490%	$94.0605	$94.06	$94.05	$94.10
7 purchase totals =	$625.96		$686.9515	$686.95	$686.95	$687.00