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	$42.55	7.848%	$45.8893	$45.89	$45.90	$45.90
Purchase #2	$82.44	12.530%	$92.7697	$92.77	$92.75	$92.80
Purchase #3	$141.78	11.660%	$158.3115	$158.31	$158.30	$158.30
Purchase #4	$149.47	13.297%	$169.345	$169.35	$169.35	$169.30
Purchase #5	$134.94	4.665%	$141.235	$141.24	$141.25	$141.20
Purchase #6	$183.59	9.102%	$200.3004	$200.30	$200.30	$200.30
Purchase #7	$112.61	4.135%	$117.2664	$117.27	$117.25	$117.30
7 purchase totals =	$847.38		$925.1173	$925.13	$925.10	$925.10