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	$68.59	5.561%	$72.4043	$72.40	$72.40	$72.40
Purchase #2	$78.84	5.153%	$82.9026	$82.90	$82.90	$82.90
Purchase #3	$92.89	7.705%	$100.0472	$100.05	$100.05	$100.00
Purchase #4	$58.51	9.340%	$63.9748	$63.97	$63.95	$64.00
Purchase #5	$66.30	5.460%	$69.92	$69.92	$69.90	$69.90
Purchase #6	$119.96	6.457%	$127.7058	$127.71	$127.70	$127.70
Purchase #7	$204.76	3.133%	$211.1751	$211.18	$211.20	$211.20
7 purchase totals =	$689.85		$728.1298	$728.13	$728.10	$728.10