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	$150.59	12.775%	$169.8279	$169.83	$169.85	$169.80
Purchase #2	$220.44	7.271%	$236.4682	$236.47	$236.45	$236.50
Purchase #3	$181.73	5.183%	$191.1491	$191.15	$191.15	$191.10
Purchase #4	$131.50	8.437%	$142.5947	$142.59	$142.60	$142.60
Purchase #5	$172.82	10.870%	$191.6055	$191.61	$191.60	$191.60
Purchase #6	$173.47	3.809%	$180.0775	$180.08	$180.10	$180.10
Purchase #7	$247.61	10.712%	$274.134	$274.13	$274.15	$274.10
7 purchase totals =	$1,278.16		$1,385.8569	$1,385.86	$1,385.90	$1,385.80