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	$33.90	12.689%	$38.2016	$38.20	$38.20	$38.20
Purchase #2	$245.71	11.722%	$274.5121	$274.51	$274.50	$274.50
Purchase #3	$191.75	11.641%	$214.0716	$214.07	$214.05	$214.10
Purchase #4	$103.91	3.459%	$107.5042	$107.50	$107.50	$107.50
Purchase #5	$131.34	11.474%	$146.41	$146.41	$146.40	$146.40
Purchase #6	$80.97	3.139%	$83.5116	$83.51	$83.50	$83.50
Purchase #7	$137.81	12.676%	$155.2788	$155.28	$155.30	$155.30
7 purchase totals =	$925.39		$1,019.4899	$1,019.48	$1,019.45	$1,019.50