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	$55.93	11.366%	$62.287	$62.29	$62.30	$62.30
Purchase #2	$145.82	9.255%	$159.3156	$159.32	$159.30	$159.30
Purchase #3	$205.36	13.853%	$233.8085	$233.81	$233.80	$233.80
Purchase #4	$52.76	12.671%	$59.4452	$59.45	$59.45	$59.40
Purchase #5	$149.48	9.783%	$164.1036	$164.10	$164.10	$164.10
Purchase #6	$231.37	9.449%	$253.2322	$253.23	$253.25	$253.20
Purchase #7	$170.33	6.137%	$180.7832	$180.78	$180.80	$180.80
7 purchase totals =	$1,011.05		$1,112.9753	$1,112.98	$1,113.00	$1,112.90