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	$210.37	11.440%	$234.4363	$234.44	$234.45	$234.40
Purchase #2	$12.89	9.215%	$14.0778	$14.08	$14.10	$14.10
Purchase #3	$116.67	12.636%	$131.4124	$131.41	$131.40	$131.40
Purchase #4	$59.46	3.797%	$61.7177	$61.72	$61.70	$61.70
Purchase #5	$138.61	10.641%	$153.3595	$153.36	$153.35	$153.40
Purchase #6	$110.62	9.253%	$120.8557	$120.86	$120.85	$120.90
Purchase #7	$73.66	6.599%	$78.5208	$78.52	$78.50	$78.50
7 purchase totals =	$722.28		$794.3802	$794.39	$794.35	$794.40