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	$97.57	12.601%	$109.8648	$109.86	$109.85	$109.90
Purchase #2	$150.93	5.506%	$159.2402	$159.24	$159.25	$159.20
Purchase #3	$189.79	5.536%	$200.2968	$200.30	$200.30	$200.30
Purchase #4	$98.97	3.119%	$102.0569	$102.06	$102.05	$102.10
Purchase #5	$128.39	8.732%	$139.601	$139.60	$139.60	$139.60
Purchase #6	$195.75	13.874%	$222.9084	$222.91	$222.90	$222.90
Purchase #7	$100.91	6.753%	$107.7245	$107.72	$107.70	$107.70
7 purchase totals =	$962.31		$1,041.6926	$1,041.69	$1,041.65	$1,041.70