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	$202.41	7.229%	$217.0422	$217.04	$217.05	$217.00
Purchase #2	$43.90	5.171%	$46.1701	$46.17	$46.15	$46.20
Purchase #3	$96.93	7.632%	$104.3277	$104.33	$104.35	$104.30
Purchase #4	$67.83	4.365%	$70.7908	$70.79	$70.80	$70.80
Purchase #5	$84.90	5.690%	$89.7308	$89.73	$89.75	$89.70
Purchase #6	$127.48	3.805%	$132.3306	$132.33	$132.35	$132.30
Purchase #7	$116.82	9.167%	$127.5289	$127.53	$127.55	$127.50
7 purchase totals =	$740.27		$787.9211	$787.92	$788.00	$787.80