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	$131.62	9.467%	$144.0805	$144.08	$144.10	$144.10
Purchase #2	$64.43	10.773%	$71.371	$71.37	$71.35	$71.40
Purchase #3	$168.59	3.155%	$173.909	$173.91	$173.90	$173.90
Purchase #4	$30.84	8.365%	$33.4198	$33.42	$33.40	$33.40
Purchase #5	$158.49	12.343%	$178.0524	$178.05	$178.05	$178.10
Purchase #6	$136.92	11.461%	$152.6124	$152.61	$152.60	$152.60
Purchase #7	$181.96	10.276%	$200.6582	$200.66	$200.65	$200.70
7 purchase totals =	$872.85		$954.1033	$954.10	$954.05	$954.20