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	$167.73	10.850%	$185.9287	$185.93	$185.95	$185.90
Purchase #2	$39.93	5.813%	$42.2511	$42.25	$42.25	$42.30
Purchase #3	$163.38	5.538%	$172.428	$172.43	$172.45	$172.40
Purchase #4	$42.77	5.190%	$44.9898	$44.99	$45.00	$45.00
Purchase #5	$155.36	9.196%	$169.6469	$169.65	$169.65	$169.60
Purchase #6	$81.79	4.103%	$85.1458	$85.15	$85.15	$85.10
Purchase #7	$114.29	4.481%	$119.4113	$119.41	$119.40	$119.40
7 purchase totals =	$765.25		$819.8016	$819.81	$819.85	$819.70