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	$165.94	4.115%	$172.7684	$172.77	$172.75	$172.80
Purchase #2	$177.38	6.279%	$188.5177	$188.52	$188.50	$188.50
Purchase #3	$168.46	12.516%	$189.5445	$189.54	$189.55	$189.50
Purchase #4	$207.81	3.750%	$215.6029	$215.60	$215.60	$215.60
Purchase #5	$57.77	7.810%	$62.2818	$62.28	$62.30	$62.30
Purchase #6	$222.37	10.512%	$245.7455	$245.75	$245.75	$245.70
Purchase #7	$20.84	12.534%	$23.4521	$23.45	$23.45	$23.50
7 purchase totals =	$1,020.57		$1,097.9129	$1,097.91	$1,097.90	$1,097.90