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	$138.28	3.630%	$143.2996	$143.30	$143.30	$143.30
Purchase #2	$143.94	10.301%	$158.7673	$158.77	$158.75	$158.80
Purchase #3	$163.32	6.620%	$174.1318	$174.13	$174.15	$174.10
Purchase #4	$216.89	7.840%	$233.8942	$233.89	$233.90	$233.90
Purchase #5	$110.60	11.280%	$123.0757	$123.08	$123.10	$123.10
Purchase #6	$179.46	6.855%	$191.762	$191.76	$191.75	$191.80
Purchase #7	$195.63	12.494%	$220.072	$220.07	$220.05	$220.10
7 purchase totals =	$1,148.12		$1,245.0026	$1,245.00	$1,245.00	$1,245.10