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	$215.62	5.504%	$227.4877	$227.49	$227.50	$227.50
Purchase #2	$133.57	8.824%	$145.3562	$145.36	$145.35	$145.40
Purchase #3	$56.33	5.504%	$59.4304	$59.43	$59.45	$59.40
Purchase #4	$243.74	6.318%	$259.1395	$259.14	$259.15	$259.10
Purchase #5	$235.65	3.379%	$243.6126	$243.61	$243.60	$243.60
Purchase #6	$6.95	13.719%	$7.9035	$7.90	$7.90	$7.90
Purchase #7	$68.80	5.779%	$72.776	$72.78	$72.80	$72.80
7 purchase totals =	$960.66		$1,015.7059	$1,015.71	$1,015.75	$1,015.70