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	$173.53	3.419%	$179.463	$179.46	$179.45	$179.50
Purchase #2	$213.36	12.870%	$240.8194	$240.82	$240.80	$240.80
Purchase #3	$207.77	7.773%	$223.92	$223.92	$223.90	$223.90
Purchase #4	$238.73	9.793%	$262.1088	$262.11	$262.10	$262.10
Purchase #5	$129.44	7.816%	$139.557	$139.56	$139.55	$139.60
Purchase #6	$54.38	5.429%	$57.3323	$57.33	$57.35	$57.30
Purchase #7	$49.43	8.312%	$53.5386	$53.54	$53.55	$53.50
7 purchase totals =	$1,066.64		$1,156.7391	$1,156.74	$1,156.70	$1,156.70