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	$116.74	10.288%	$128.7502	$128.75	$128.75	$128.80
Purchase #2	$244.28	6.153%	$259.3105	$259.31	$259.30	$259.30
Purchase #3	$78.73	9.841%	$86.4778	$86.48	$86.50	$86.50
Purchase #4	$93.75	4.127%	$97.6191	$97.62	$97.60	$97.60
Purchase #5	$85.48	5.818%	$90.4532	$90.45	$90.45	$90.50
Purchase #6	$132.81	7.767%	$143.1254	$143.13	$143.15	$143.10
Purchase #7	$78.52	11.428%	$87.4933	$87.49	$87.50	$87.50
7 purchase totals =	$830.31		$893.2295	$893.23	$893.25	$893.30