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	$55.49	11.505%	$61.8741	$61.87	$61.85	$61.90
Purchase #2	$62.63	8.442%	$67.9172	$67.92	$67.90	$67.90
Purchase #3	$166.57	9.168%	$181.8411	$181.84	$181.85	$181.80
Purchase #4	$58.65	7.179%	$62.8605	$62.86	$62.85	$62.90
Purchase #5	$82.94	6.561%	$88.3817	$88.38	$88.40	$88.40
Purchase #6	$80.57	7.740%	$86.8061	$86.81	$86.80	$86.80
Purchase #7	$224.47	12.404%	$252.3133	$252.31	$252.30	$252.30
7 purchase totals =	$731.32		$801.9940	$801.99	$801.95	$802.00