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	$130.60	8.598%	$141.829	$141.83	$141.85	$141.80
Purchase #2	$194.27	9.781%	$213.2715	$213.27	$213.25	$213.30
Purchase #3	$210.50	11.808%	$235.3558	$235.36	$235.35	$235.40
Purchase #4	$245.68	12.196%	$275.6431	$275.64	$275.65	$275.60
Purchase #5	$157.93	6.704%	$168.5176	$168.52	$168.50	$168.50
Purchase #6	$72.83	11.460%	$81.1763	$81.18	$81.20	$81.20
Purchase #7	$192.52	3.611%	$199.4719	$199.47	$199.45	$199.50
7 purchase totals =	$1,204.33		$1,315.2652	$1,315.27	$1,315.25	$1,315.30