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	$109.41	8.607%	$118.8269	$118.83	$118.85	$118.80
Purchase #2	$76.59	12.530%	$86.1867	$86.19	$86.20	$86.20
Purchase #3	$92.65	7.151%	$99.2754	$99.28	$99.30	$99.30
Purchase #4	$108.27	3.201%	$111.7357	$111.74	$111.75	$111.70
Purchase #5	$219.94	9.795%	$241.4831	$241.48	$241.50	$241.50
Purchase #6	$43.72	7.240%	$46.8853	$46.89	$46.90	$46.90
Purchase #7	$74.46	11.218%	$82.8129	$82.81	$82.80	$82.80
7 purchase totals =	$725.04		$787.2060	$787.22	$787.30	$787.20