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	$242.92	12.677%	$273.715	$273.72	$273.70	$273.70
Purchase #2	$42.31	13.473%	$48.0104	$48.01	$48.00	$48.00
Purchase #3	$51.45	3.711%	$53.3593	$53.36	$53.35	$53.40
Purchase #4	$56.83	9.316%	$62.1243	$62.12	$62.10	$62.10
Purchase #5	$95.33	3.233%	$98.412	$98.41	$98.40	$98.40
Purchase #6	$189.92	11.166%	$211.1265	$211.13	$211.15	$211.10
Purchase #7	$13.69	5.688%	$14.4687	$14.47	$14.45	$14.50
7 purchase totals =	$692.45		$761.2162	$761.22	$761.15	$761.20