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	$72.83	6.418%	$77.5042	$77.50	$77.50	$77.50
Purchase #2	$111.58	7.301%	$119.7265	$119.73	$119.75	$119.70
Purchase #3	$192.48	12.418%	$216.3822	$216.38	$216.40	$216.40
Purchase #4	$139.55	12.292%	$156.7035	$156.70	$156.70	$156.70
Purchase #5	$199.47	3.305%	$206.0625	$206.06	$206.05	$206.10
Purchase #6	$83.51	3.357%	$86.3134	$86.31	$86.30	$86.30
Purchase #7	$128.64	13.137%	$145.5394	$145.54	$145.55	$145.50
7 purchase totals =	$928.06		$1,008.2317	$1,008.22	$1,008.25	$1,008.20