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	$38.69	11.191%	$43.0198	$43.02	$43.00	$43.00
Purchase #2	$107.56	3.738%	$111.5806	$111.58	$111.60	$111.60
Purchase #3	$153.41	8.812%	$166.9285	$166.93	$166.95	$166.90
Purchase #4	$79.25	6.711%	$84.5685	$84.57	$84.55	$84.60
Purchase #5	$114.27	8.416%	$123.887	$123.89	$123.90	$123.90
Purchase #6	$245.96	12.847%	$277.5585	$277.56	$277.55	$277.60
Purchase #7	$50.49	3.315%	$52.1637	$52.16	$52.15	$52.20
7 purchase totals =	$789.63		$859.7066	$859.71	$859.70	$859.80