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	$175.43	9.644%	$192.3485	$192.35	$192.35	$192.30
Purchase #2	$249.93	8.127%	$270.2418	$270.24	$270.25	$270.20
Purchase #3	$31.59	6.457%	$33.6298	$33.63	$33.65	$33.60
Purchase #4	$133.69	6.828%	$142.8184	$142.82	$142.80	$142.80
Purchase #5	$40.56	4.219%	$42.2712	$42.27	$42.25	$42.30
Purchase #6	$18.41	4.504%	$19.2392	$19.24	$19.25	$19.20
Purchase #7	$92.69	9.500%	$101.4956	$101.50	$101.50	$101.50
7 purchase totals =	$742.30		$802.0445	$802.05	$802.05	$801.90