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	$231.38	13.788%	$263.2827	$263.28	$263.30	$263.30
Purchase #2	$94.44	10.748%	$104.5904	$104.59	$104.60	$104.60
Purchase #3	$185.45	10.106%	$204.1916	$204.19	$204.20	$204.20
Purchase #4	$77.53	6.286%	$82.4035	$82.40	$82.40	$82.40
Purchase #5	$52.99	12.778%	$59.7611	$59.76	$59.75	$59.80
Purchase #6	$192.35	9.343%	$210.3213	$210.32	$210.30	$210.30
Purchase #7	$171.78	5.221%	$180.7486	$180.75	$180.75	$180.70
7 purchase totals =	$1,005.92		$1,105.2992	$1,105.29	$1,105.30	$1,105.30