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	$171.46	12.232%	$192.433	$192.43	$192.45	$192.40
Purchase #2	$238.78	12.107%	$267.6891	$267.69	$267.70	$267.70
Purchase #3	$166.93	11.446%	$186.0368	$186.04	$186.05	$186.00
Purchase #4	$79.38	9.460%	$86.8893	$86.89	$86.90	$86.90
Purchase #5	$147.63	5.421%	$155.633	$155.63	$155.65	$155.60
Purchase #6	$127.31	13.723%	$144.7808	$144.78	$144.80	$144.80
Purchase #7	$89.48	12.510%	$100.6739	$100.67	$100.65	$100.70
7 purchase totals =	$1,020.97		$1,134.1359	$1,134.13	$1,134.20	$1,134.10