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	$143.68	7.633%	$154.6471	$154.65	$154.65	$154.60
Purchase #2	$76.44	9.558%	$83.7461	$83.75	$83.75	$83.70
Purchase #3	$250.91	11.399%	$279.5112	$279.51	$279.50	$279.50
Purchase #4	$215.29	10.795%	$238.5306	$238.53	$238.55	$238.50
Purchase #5	$80.57	10.357%	$88.9146	$88.91	$88.90	$88.90
Purchase #6	$153.27	7.594%	$164.9093	$164.91	$164.90	$164.90
Purchase #7	$173.31	13.192%	$196.1731	$196.17	$196.15	$196.20
7 purchase totals =	$1,093.47		$1,206.4320	$1,206.43	$1,206.40	$1,206.30