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	$179.76	6.780%	$191.9477	$191.95	$191.95	$191.90
Purchase #2	$79.59	8.407%	$86.2811	$86.28	$86.30	$86.30
Purchase #3	$224.67	5.703%	$237.4829	$237.48	$237.50	$237.50
Purchase #4	$249.50	10.811%	$276.4734	$276.47	$276.45	$276.50
Purchase #5	$158.40	9.131%	$172.8635	$172.86	$172.85	$172.90
Purchase #6	$108.68	6.818%	$116.0898	$116.09	$116.10	$116.10
Purchase #7	$202.71	12.337%	$227.7183	$227.72	$227.70	$227.70
7 purchase totals =	$1,203.31		$1,308.8567	$1,308.85	$1,308.85	$1,308.90