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	$137.51	10.676%	$152.1906	$152.19	$152.20	$152.20
Purchase #2	$144.28	12.615%	$162.4809	$162.48	$162.50	$162.50
Purchase #3	$64.70	12.764%	$72.9583	$72.96	$72.95	$73.00
Purchase #4	$60.74	13.762%	$69.099	$69.10	$69.10	$69.10
Purchase #5	$179.96	4.745%	$188.4991	$188.50	$188.50	$188.50
Purchase #6	$146.95	5.808%	$155.4849	$155.48	$155.50	$155.50
Purchase #7	$148.25	3.487%	$153.4195	$153.42	$153.40	$153.40
7 purchase totals =	$882.39		$954.1323	$954.13	$954.15	$954.20