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	$87.89	12.217%	$98.6275	$98.63	$98.65	$98.60
Purchase #2	$214.38	13.841%	$244.0523	$244.05	$244.05	$244.10
Purchase #3	$127.88	8.781%	$139.1091	$139.11	$139.10	$139.10
Purchase #4	$54.25	4.544%	$56.7151	$56.72	$56.70	$56.70
Purchase #5	$65.99	8.399%	$71.5325	$71.53	$71.55	$71.50
Purchase #6	$176.31	11.548%	$196.6703	$196.67	$196.65	$196.70
Purchase #7	$225.91	10.782%	$250.2676	$250.27	$250.25	$250.30
7 purchase totals =	$952.61		$1,056.9744	$1,056.98	$1,056.95	$1,057.00