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	$101.40	9.648%	$111.1831	$111.18	$111.20	$111.20
Purchase #2	$119.76	9.609%	$131.2677	$131.27	$131.25	$131.30
Purchase #3	$72.98	12.789%	$82.3134	$82.31	$82.30	$82.30
Purchase #4	$137.30	7.783%	$147.9861	$147.99	$148.00	$148.00
Purchase #5	$196.35	6.145%	$208.4157	$208.42	$208.40	$208.40
Purchase #6	$12.33	12.686%	$13.8942	$13.89	$13.90	$13.90
Purchase #7	$187.80	5.529%	$198.1835	$198.18	$198.20	$198.20
7 purchase totals =	$827.92		$893.2437	$893.24	$893.25	$893.30