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	$171.84	11.193%	$191.0741	$191.07	$191.05	$191.10
Purchase #2	$86.42	4.297%	$90.1335	$90.13	$90.15	$90.10
Purchase #3	$73.98	12.608%	$83.3074	$83.31	$83.30	$83.30
Purchase #4	$243.72	12.538%	$274.2776	$274.28	$274.30	$274.30
Purchase #5	$198.46	12.122%	$222.5173	$222.52	$222.50	$222.50
Purchase #6	$205.90	7.186%	$220.696	$220.70	$220.70	$220.70
Purchase #7	$23.68	7.645%	$25.4903	$25.49	$25.50	$25.50
7 purchase totals =	$1,004.00		$1,107.4962	$1,107.50	$1,107.50	$1,107.50