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	$59.40	9.839%	$65.2444	$65.24	$65.25	$65.20
Purchase #2	$165.45	3.789%	$171.7189	$171.72	$171.70	$171.70
Purchase #3	$195.65	6.560%	$208.4846	$208.48	$208.50	$208.50
Purchase #4	$210.69	7.833%	$227.1933	$227.19	$227.20	$227.20
Purchase #5	$139.92	8.498%	$151.8104	$151.81	$151.80	$151.80
Purchase #6	$241.44	7.462%	$259.4563	$259.46	$259.45	$259.50
Purchase #7	$59.25	3.262%	$61.1827	$61.18	$61.20	$61.20
7 purchase totals =	$1,071.80		$1,145.0906	$1,145.08	$1,145.10	$1,145.10