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	$89.71	5.140%	$94.3211	$94.32	$94.30	$94.30
Purchase #2	$180.76	5.814%	$191.2694	$191.27	$191.25	$191.30
Purchase #3	$168.97	3.249%	$174.4598	$174.46	$174.45	$174.50
Purchase #4	$89.76	5.164%	$94.3952	$94.40	$94.40	$94.40
Purchase #5	$104.71	4.800%	$109.7361	$109.74	$109.75	$109.70
Purchase #6	$59.52	10.173%	$65.575	$65.58	$65.60	$65.60
Purchase #7	$116.79	13.396%	$132.4352	$132.44	$132.45	$132.40
7 purchase totals =	$810.22		$862.1918	$862.21	$862.20	$862.20