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	$86.47	9.299%	$94.5108	$94.51	$94.50	$94.50
Purchase #2	$43.44	8.286%	$47.0394	$47.04	$47.05	$47.00
Purchase #3	$92.33	8.681%	$100.3452	$100.35	$100.35	$100.30
Purchase #4	$155.65	10.500%	$171.9933	$171.99	$172.00	$172.00
Purchase #5	$38.40	5.695%	$40.5869	$40.59	$40.60	$40.60
Purchase #6	$180.26	5.403%	$189.9994	$190.00	$190.00	$190.00
Purchase #7	$79.39	12.681%	$89.4574	$89.46	$89.45	$89.50
7 purchase totals =	$675.94		$733.9324	$733.94	$733.95	$733.90