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	$158.56	4.853%	$166.2549	$166.25	$166.25	$166.30
Purchase #2	$137.60	11.424%	$153.3194	$153.32	$153.30	$153.30
Purchase #3	$215.96	11.698%	$241.223	$241.22	$241.20	$241.20
Purchase #4	$191.82	12.287%	$215.3889	$215.39	$215.40	$215.40
Purchase #5	$7.89	11.695%	$8.8127	$8.81	$8.80	$8.80
Purchase #6	$224.95	11.333%	$250.4436	$250.44	$250.45	$250.40
Purchase #7	$187.82	6.271%	$199.5982	$199.60	$199.60	$199.60
7 purchase totals =	$1,124.60		$1,235.0407	$1,235.03	$1,235.00	$1,235.00