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	$238.89	9.254%	$260.9969	$261.00	$261.00	$261.00
Purchase #2	$40.98	9.599%	$44.9137	$44.91	$44.90	$44.90
Purchase #3	$74.61	12.277%	$83.7699	$83.77	$83.75	$83.80
Purchase #4	$130.86	12.591%	$147.3366	$147.34	$147.35	$147.30
Purchase #5	$250.60	7.712%	$269.9263	$269.93	$269.95	$269.90
Purchase #6	$41.65	5.426%	$43.9099	$43.91	$43.90	$43.90
Purchase #7	$176.30	13.161%	$199.5028	$199.50	$199.50	$199.50
7 purchase totals =	$953.89		$1,050.3561	$1,050.36	$1,050.35	$1,050.30