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	$181.34	6.378%	$192.9059	$192.91	$192.90	$192.90
Purchase #2	$243.88	9.263%	$266.4706	$266.47	$266.45	$266.50
Purchase #3	$241.83	13.805%	$275.2146	$275.21	$275.20	$275.20
Purchase #4	$131.54	12.463%	$147.9338	$147.93	$147.95	$147.90
Purchase #5	$55.51	12.121%	$62.2384	$62.24	$62.25	$62.20
Purchase #6	$27.75	5.641%	$29.3154	$29.32	$29.30	$29.30
Purchase #7	$116.63	5.846%	$123.4482	$123.45	$123.45	$123.40
7 purchase totals =	$998.48		$1,097.5269	$1,097.53	$1,097.50	$1,097.40