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	$32.80	11.743%	$36.6517	$36.65	$36.65	$36.70
Purchase #2	$173.42	3.423%	$179.3562	$179.36	$179.35	$179.40
Purchase #3	$231.32	6.739%	$246.9087	$246.91	$246.90	$246.90
Purchase #4	$84.46	5.830%	$89.384	$89.38	$89.40	$89.40
Purchase #5	$42.36	6.317%	$45.0359	$45.04	$45.05	$45.00
Purchase #6	$219.76	9.202%	$239.9823	$239.98	$240.00	$240.00
Purchase #7	$25.77	10.537%	$28.4854	$28.49	$28.50	$28.50
7 purchase totals =	$809.89		$865.8042	$865.81	$865.85	$865.90