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	$40.59	4.206%	$42.2972	$42.30	$42.30	$42.30
Purchase #2	$79.55	3.556%	$82.3788	$82.38	$82.40	$82.40
Purchase #3	$130.66	4.368%	$136.3672	$136.37	$136.35	$136.40
Purchase #4	$217.41	7.168%	$232.9939	$232.99	$233.00	$233.00
Purchase #5	$7.87	6.379%	$8.372	$8.37	$8.35	$8.40
Purchase #6	$187.32	4.818%	$196.3451	$196.35	$196.35	$196.30
Purchase #7	$86.33	13.839%	$98.2772	$98.28	$98.30	$98.30
7 purchase totals =	$749.73		$797.0314	$797.04	$797.05	$797.10