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	$211.73	5.867%	$224.1522	$224.15	$224.15	$224.20
Purchase #2	$172.52	7.189%	$184.9225	$184.92	$184.90	$184.90
Purchase #3	$210.95	4.190%	$219.7888	$219.79	$219.80	$219.80
Purchase #4	$91.88	6.401%	$97.7612	$97.76	$97.75	$97.80
Purchase #5	$79.73	7.360%	$85.5981	$85.60	$85.60	$85.60
Purchase #6	$135.71	6.856%	$145.0143	$145.01	$145.00	$145.00
Purchase #7	$53.45	10.868%	$59.2589	$59.26	$59.25	$59.30
7 purchase totals =	$955.97		$1,016.4960	$1,016.49	$1,016.45	$1,016.60