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	$97.67	13.177%	$110.54	$110.54	$110.55	$110.50
Purchase #2	$205.34	8.318%	$222.4202	$222.42	$222.40	$222.40
Purchase #3	$74.89	9.848%	$82.2652	$82.27	$82.25	$82.30
Purchase #4	$118.93	7.369%	$127.694	$127.69	$127.70	$127.70
Purchase #5	$247.78	4.741%	$259.5272	$259.53	$259.55	$259.50
Purchase #6	$113.62	12.452%	$127.768	$127.77	$127.75	$127.80
Purchase #7	$169.88	5.413%	$179.0756	$179.08	$179.10	$179.10
7 purchase totals =	$1,028.11		$1,109.2902	$1,109.30	$1,109.30	$1,109.30