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	$92.33	11.272%	$102.7374	$102.74	$102.75	$102.70
Purchase #2	$188.30	6.273%	$200.1121	$200.11	$200.10	$200.10
Purchase #3	$191.89	6.628%	$204.6085	$204.61	$204.60	$204.60
Purchase #4	$209.77	3.816%	$217.7748	$217.77	$217.75	$217.80
Purchase #5	$120.82	13.105%	$136.6535	$136.65	$136.65	$136.70
Purchase #6	$9.31	10.643%	$10.3009	$10.30	$10.30	$10.30
Purchase #7	$120.29	9.459%	$131.6682	$131.67	$131.65	$131.70
7 purchase totals =	$932.71		$1,003.8554	$1,003.85	$1,003.80	$1,003.90