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	$143.83	12.541%	$161.8677	$161.87	$161.85	$161.90
Purchase #2	$128.56	8.324%	$139.2613	$139.26	$139.25	$139.30
Purchase #3	$229.88	3.552%	$238.0453	$238.05	$238.05	$238.00
Purchase #4	$144.52	12.183%	$162.1269	$162.13	$162.15	$162.10
Purchase #5	$99.35	6.118%	$105.4282	$105.43	$105.45	$105.40
Purchase #6	$143.63	12.737%	$161.9242	$161.92	$161.90	$161.90
Purchase #7	$41.57	4.411%	$43.4037	$43.40	$43.40	$43.40
7 purchase totals =	$931.34		$1,012.0573	$1,012.06	$1,012.05	$1,012.00