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	$151.56	11.333%	$168.7363	$168.74	$168.75	$168.70
Purchase #2	$78.61	7.623%	$84.6024	$84.60	$84.60	$84.60
Purchase #3	$98.31	11.856%	$109.9656	$109.97	$109.95	$110.00
Purchase #4	$112.71	4.690%	$117.9961	$118.00	$118.00	$118.00
Purchase #5	$37.65	12.800%	$42.4692	$42.47	$42.45	$42.50
Purchase #6	$108.72	7.112%	$116.4522	$116.45	$116.45	$116.50
Purchase #7	$198.56	6.232%	$210.9343	$210.93	$210.95	$210.90
7 purchase totals =	$786.12		$851.1561	$851.16	$851.15	$851.20