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	$24.56	4.299%	$25.6158	$25.62	$25.60	$25.60
Purchase #2	$180.59	4.596%	$188.8899	$188.89	$188.90	$188.90
Purchase #3	$220.69	4.137%	$229.8199	$229.82	$229.80	$229.80
Purchase #4	$162.50	6.609%	$173.2396	$173.24	$173.25	$173.20
Purchase #5	$89.44	3.793%	$92.8325	$92.83	$92.85	$92.80
Purchase #6	$134.26	8.295%	$145.3969	$145.40	$145.40	$145.40
Purchase #7	$55.56	7.573%	$59.7676	$59.77	$59.75	$59.80
7 purchase totals =	$867.60		$915.5622	$915.57	$915.55	$915.50