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	$47.68	9.404%	$52.1638	$52.16	$52.15	$52.20
Purchase #2	$139.83	9.267%	$152.788	$152.79	$152.80	$152.80
Purchase #3	$238.25	11.454%	$265.5392	$265.54	$265.55	$265.50
Purchase #4	$124.50	9.544%	$136.3823	$136.38	$136.40	$136.40
Purchase #5	$55.39	9.222%	$60.4981	$60.50	$60.50	$60.50
Purchase #6	$118.33	5.179%	$124.4583	$124.46	$124.45	$124.50
Purchase #7	$171.50	4.370%	$178.9946	$178.99	$179.00	$179.00
7 purchase totals =	$895.48		$970.8243	$970.82	$970.85	$970.90