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	$212.99	5.352%	$224.3892	$224.39	$224.40	$224.40
Purchase #2	$191.74	12.325%	$215.372	$215.37	$215.35	$215.40
Purchase #3	$208.34	11.243%	$231.7637	$231.76	$231.75	$231.80
Purchase #4	$45.56	11.109%	$50.6213	$50.62	$50.60	$50.60
Purchase #5	$17.90	11.792%	$20.0108	$20.01	$20.00	$20.00
Purchase #6	$184.28	10.846%	$204.267	$204.27	$204.25	$204.30
Purchase #7	$99.33	3.703%	$103.0082	$103.01	$103.00	$103.00
7 purchase totals =	$960.14		$1,049.4322	$1,049.43	$1,049.35	$1,049.50