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	$131.98	4.607%	$138.0603	$138.06	$138.05	$138.10
Purchase #2	$218.47	11.333%	$243.2292	$243.23	$243.25	$243.20
Purchase #3	$171.79	3.449%	$177.715	$177.72	$177.70	$177.70
Purchase #4	$53.40	11.456%	$59.5175	$59.52	$59.50	$59.50
Purchase #5	$53.61	12.812%	$60.4785	$60.48	$60.50	$60.50
Purchase #6	$215.34	4.377%	$224.7654	$224.77	$224.75	$224.80
Purchase #7	$166.29	3.226%	$171.6545	$171.65	$171.65	$171.70
7 purchase totals =	$1,010.88		$1,075.4204	$1,075.43	$1,075.40	$1,075.50