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	$13.73	11.719%	$15.339	$15.34	$15.35	$15.30
Purchase #2	$84.38	6.581%	$89.933	$89.93	$89.95	$89.90
Purchase #3	$26.79	3.873%	$27.8276	$27.83	$27.85	$27.80
Purchase #4	$41.33	5.749%	$43.7061	$43.71	$43.70	$43.70
Purchase #5	$204.81	3.524%	$212.0275	$212.03	$212.05	$212.00
Purchase #6	$127.38	9.303%	$139.2302	$139.23	$139.25	$139.20
Purchase #7	$160.36	12.632%	$180.6167	$180.62	$180.60	$180.60
7 purchase totals =	$658.78		$708.6801	$708.69	$708.75	$708.50