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	$29.35	3.832%	$30.4747	$30.47	$30.45	$30.50
Purchase #2	$199.86	6.758%	$213.3665	$213.37	$213.35	$213.40
Purchase #3	$152.62	3.858%	$158.5081	$158.51	$158.50	$158.50
Purchase #4	$233.42	3.844%	$242.3927	$242.39	$242.40	$242.40
Purchase #5	$179.88	6.703%	$191.9374	$191.94	$191.95	$191.90
Purchase #6	$83.41	5.774%	$88.2261	$88.23	$88.25	$88.20
Purchase #7	$165.78	11.515%	$184.8696	$184.87	$184.85	$184.90
7 purchase totals =	$1,044.32		$1,109.7751	$1,109.78	$1,109.75	$1,109.80