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	$227.78	4.497%	$238.0233	$238.02	$238.00	$238.00
Purchase #2	$177.72	4.854%	$186.3465	$186.35	$186.35	$186.30
Purchase #3	$94.41	11.532%	$105.2974	$105.30	$105.30	$105.30
Purchase #4	$98.29	11.462%	$109.556	$109.56	$109.55	$109.60
Purchase #5	$170.90	9.871%	$187.7695	$187.77	$187.75	$187.80
Purchase #6	$147.38	12.166%	$165.3103	$165.31	$165.30	$165.30
Purchase #7	$108.56	7.376%	$116.5674	$116.57	$116.55	$116.60
7 purchase totals =	$1,025.04		$1,108.8704	$1,108.88	$1,108.80	$1,108.90