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	$123.76	8.704%	$134.5321	$134.53	$134.55	$134.50
Purchase #2	$185.62	13.286%	$210.2815	$210.28	$210.30	$210.30
Purchase #3	$141.43	11.643%	$157.8967	$157.90	$157.90	$157.90
Purchase #4	$171.96	10.227%	$189.5463	$189.55	$189.55	$189.50
Purchase #5	$161.98	3.349%	$167.4047	$167.40	$167.40	$167.40
Purchase #6	$104.28	13.704%	$118.5705	$118.57	$118.55	$118.60
Purchase #7	$95.83	13.278%	$108.5543	$108.55	$108.55	$108.60
7 purchase totals =	$984.86		$1,086.7861	$1,086.78	$1,086.80	$1,086.80