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	$116.71	10.447%	$128.9027	$128.90	$128.90	$128.90
Purchase #2	$81.46	13.308%	$92.3007	$92.30	$92.30	$92.30
Purchase #3	$9.37	8.593%	$10.1752	$10.18	$10.20	$10.20
Purchase #4	$245.55	11.218%	$273.0958	$273.10	$273.10	$273.10
Purchase #5	$248.74	13.591%	$282.5463	$282.55	$282.55	$282.50
Purchase #6	$134.28	7.431%	$144.2583	$144.26	$144.25	$144.30
Purchase #7	$175.89	13.597%	$199.8058	$199.81	$199.80	$199.80
7 purchase totals =	$1,012.00		$1,131.0848	$1,131.10	$1,131.10	$1,131.10