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	$100.50	9.369%	$109.9158	$109.92	$109.90	$109.90
Purchase #2	$191.62	4.823%	$200.8618	$200.86	$200.85	$200.90
Purchase #3	$224.32	3.799%	$232.8419	$232.84	$232.85	$232.80
Purchase #4	$130.40	9.673%	$143.0136	$143.01	$143.00	$143.00
Purchase #5	$103.39	6.103%	$109.6999	$109.70	$109.70	$109.70
Purchase #6	$187.99	12.834%	$212.1166	$212.12	$212.10	$212.10
Purchase #7	$109.95	8.669%	$119.4816	$119.48	$119.50	$119.50
7 purchase totals =	$1,048.17		$1,127.9312	$1,127.93	$1,127.90	$1,127.90