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	$108.27	7.874%	$116.7952	$116.80	$116.80	$116.80
Purchase #2	$210.60	3.639%	$218.2637	$218.26	$218.25	$218.30
Purchase #3	$13.63	11.808%	$15.2394	$15.24	$15.25	$15.20
Purchase #4	$160.56	6.784%	$171.4524	$171.45	$171.45	$171.50
Purchase #5	$112.88	10.144%	$124.3305	$124.33	$124.35	$124.30
Purchase #6	$85.79	11.828%	$95.9372	$95.94	$95.95	$95.90
Purchase #7	$104.40	4.433%	$109.0281	$109.03	$109.05	$109.00
7 purchase totals =	$796.13		$851.0465	$851.05	$851.10	$851.00