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	$103.72	6.753%	$110.7242	$110.72	$110.70	$110.70
Purchase #2	$88.43	4.796%	$92.6711	$92.67	$92.65	$92.70
Purchase #3	$169.35	7.201%	$181.5449	$181.54	$181.55	$181.50
Purchase #4	$38.29	4.622%	$40.0598	$40.06	$40.05	$40.10
Purchase #5	$38.46	11.842%	$43.0144	$43.01	$43.00	$43.00
Purchase #6	$42.70	4.530%	$44.6343	$44.63	$44.65	$44.60
Purchase #7	$179.66	4.212%	$187.2273	$187.23	$187.25	$187.20
7 purchase totals =	$660.61		$699.8760	$699.86	$699.85	$699.80