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	$145.98	11.246%	$162.3969	$162.40	$162.40	$162.40
Purchase #2	$232.45	8.361%	$251.8851	$251.89	$251.90	$251.90
Purchase #3	$144.59	12.190%	$162.2155	$162.22	$162.20	$162.20
Purchase #4	$174.45	7.698%	$187.8792	$187.88	$187.90	$187.90
Purchase #5	$192.76	10.192%	$212.4061	$212.41	$212.40	$212.40
Purchase #6	$185.61	3.234%	$191.6126	$191.61	$191.60	$191.60
Purchase #7	$163.82	5.537%	$172.8907	$172.89	$172.90	$172.90
7 purchase totals =	$1,239.66		$1,341.2861	$1,341.30	$1,341.30	$1,341.30