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	$93.70	10.694%	$103.7203	$103.72	$103.70	$103.70
Purchase #2	$205.76	4.154%	$214.3073	$214.31	$214.30	$214.30
Purchase #3	$81.35	9.270%	$88.8911	$88.89	$88.90	$88.90
Purchase #4	$79.56	9.134%	$86.827	$86.83	$86.85	$86.80
Purchase #5	$87.72	13.346%	$99.4271	$99.43	$99.45	$99.40
Purchase #6	$109.81	6.817%	$117.2957	$117.30	$117.30	$117.30
Purchase #7	$90.76	9.367%	$99.2615	$99.26	$99.25	$99.30
7 purchase totals =	$748.66		$809.7300	$809.74	$809.75	$809.70