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	$211.98	13.870%	$241.3816	$241.38	$241.40	$241.40
Purchase #2	$53.50	9.629%	$58.6515	$58.65	$58.65	$58.70
Purchase #3	$86.97	4.492%	$90.8767	$90.88	$90.90	$90.90
Purchase #4	$43.84	3.643%	$45.4371	$45.44	$45.45	$45.40
Purchase #5	$82.88	4.825%	$86.879	$86.88	$86.90	$86.90
Purchase #6	$222.42	9.595%	$243.7612	$243.76	$243.75	$243.80
Purchase #7	$147.54	4.535%	$154.2309	$154.23	$154.25	$154.20
7 purchase totals =	$849.13		$921.2180	$921.22	$921.30	$921.30