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	$32.83	5.333%	$34.5808	$34.58	$34.60	$34.60
Purchase #2	$20.69	10.464%	$22.855	$22.86	$22.85	$22.90
Purchase #3	$122.72	12.316%	$137.8342	$137.83	$137.85	$137.80
Purchase #4	$128.88	9.486%	$141.1056	$141.11	$141.10	$141.10
Purchase #5	$174.36	13.145%	$197.2796	$197.28	$197.30	$197.30
Purchase #6	$62.97	7.179%	$67.4906	$67.49	$67.50	$67.50
Purchase #7	$65.86	3.144%	$67.9306	$67.93	$67.95	$67.90
7 purchase totals =	$608.31		$669.0764	$669.08	$669.15	$669.10