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	$200.73	13.781%	$228.3926	$228.39	$228.40	$228.40
Purchase #2	$68.49	5.278%	$72.1049	$72.10	$72.10	$72.10
Purchase #3	$147.44	13.665%	$167.5877	$167.59	$167.60	$167.60
Purchase #4	$109.56	12.803%	$123.587	$123.59	$123.60	$123.60
Purchase #5	$104.60	3.845%	$108.6219	$108.62	$108.60	$108.60
Purchase #6	$144.89	3.582%	$150.08	$150.08	$150.10	$150.10
Purchase #7	$88.43	3.565%	$91.5825	$91.58	$91.60	$91.60
7 purchase totals =	$864.14		$941.9566	$941.95	$942.00	$942.00