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	$41.59	9.736%	$45.6392	$45.64	$45.65	$45.60
Purchase #2	$209.33	5.655%	$221.1676	$221.17	$221.15	$221.20
Purchase #3	$198.94	8.363%	$215.5774	$215.58	$215.60	$215.60
Purchase #4	$39.99	8.506%	$43.3915	$43.39	$43.40	$43.40
Purchase #5	$47.31	6.164%	$50.2262	$50.23	$50.25	$50.20
Purchase #6	$36.94	5.253%	$38.8805	$38.88	$38.90	$38.90
Purchase #7	$101.95	12.735%	$114.9333	$114.93	$114.95	$114.90
7 purchase totals =	$676.05		$729.8157	$729.82	$729.90	$729.80