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	$123.64	6.549%	$131.7372	$131.74	$131.75	$131.70
Purchase #2	$250.56	6.666%	$267.2623	$267.26	$267.25	$267.30
Purchase #3	$97.31	4.262%	$101.4574	$101.46	$101.45	$101.50
Purchase #4	$28.94	10.323%	$31.9275	$31.93	$31.95	$31.90
Purchase #5	$145.58	5.173%	$153.1109	$153.11	$153.10	$153.10
Purchase #6	$8.61	13.699%	$9.7895	$9.79	$9.80	$9.80
Purchase #7	$52.96	11.816%	$59.2178	$59.22	$59.20	$59.20
7 purchase totals =	$707.60		$754.5026	$754.51	$754.50	$754.50