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	$124.67	6.720%	$133.0478	$133.05	$133.05	$133.00
Purchase #2	$193.51	11.310%	$215.396	$215.40	$215.40	$215.40
Purchase #3	$179.46	11.543%	$200.1751	$200.18	$200.20	$200.20
Purchase #4	$230.75	4.559%	$241.2699	$241.27	$241.25	$241.30
Purchase #5	$40.70	3.640%	$42.1815	$42.18	$42.20	$42.20
Purchase #6	$168.48	13.402%	$191.0597	$191.06	$191.05	$191.10
Purchase #7	$74.32	10.369%	$82.0262	$82.03	$82.05	$82.00
7 purchase totals =	$1,011.89		$1,105.1562	$1,105.17	$1,105.20	$1,105.20