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	$134.79	10.292%	$148.6626	$148.66	$148.65	$148.70
Purchase #2	$41.32	3.776%	$42.8802	$42.88	$42.90	$42.90
Purchase #3	$155.32	4.727%	$162.662	$162.66	$162.65	$162.70
Purchase #4	$198.72	13.488%	$225.5234	$225.52	$225.50	$225.50
Purchase #5	$12.89	4.439%	$13.4622	$13.46	$13.45	$13.50
Purchase #6	$63.66	7.159%	$68.2174	$68.22	$68.20	$68.20
Purchase #7	$40.89	3.133%	$42.1711	$42.17	$42.15	$42.20
7 purchase totals =	$647.59		$703.5789	$703.57	$703.50	$703.70