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	$59.94	3.524%	$62.0523	$62.05	$62.05	$62.10
Purchase #2	$42.90	9.419%	$46.9408	$46.94	$46.95	$46.90
Purchase #3	$38.92	12.216%	$43.6745	$43.67	$43.65	$43.70
Purchase #4	$149.27	11.443%	$166.351	$166.35	$166.35	$166.40
Purchase #5	$193.31	9.614%	$211.8948	$211.89	$211.90	$211.90
Purchase #6	$27.88	12.845%	$31.4612	$31.46	$31.45	$31.50
Purchase #7	$242.59	5.296%	$255.4376	$255.44	$255.45	$255.40
7 purchase totals =	$754.81		$817.8122	$817.80	$817.80	$817.90