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	$55.38	11.650%	$61.8318	$61.83	$61.85	$61.80
Purchase #2	$200.92	11.114%	$223.2502	$223.25	$223.25	$223.30
Purchase #3	$13.43	6.250%	$14.2694	$14.27	$14.25	$14.30
Purchase #4	$174.77	12.363%	$196.3768	$196.38	$196.40	$196.40
Purchase #5	$153.72	11.724%	$171.7421	$171.74	$171.75	$171.70
Purchase #6	$133.38	8.552%	$144.7867	$144.79	$144.80	$144.80
Purchase #7	$6.33	12.812%	$7.141	$7.14	$7.15	$7.10
7 purchase totals =	$737.93		$819.3980	$819.40	$819.45	$819.40