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	$155.94	5.439%	$164.4216	$164.42	$164.40	$164.40
Purchase #2	$55.44	6.847%	$59.236	$59.24	$59.25	$59.20
Purchase #3	$94.89	6.672%	$101.2211	$101.22	$101.20	$101.20
Purchase #4	$77.42	6.858%	$82.7295	$82.73	$82.75	$82.70
Purchase #5	$99.73	13.269%	$112.9632	$112.96	$112.95	$113.00
Purchase #6	$156.85	6.179%	$166.5418	$166.54	$166.55	$166.50
Purchase #7	$127.53	4.113%	$132.7753	$132.78	$132.80	$132.80
7 purchase totals =	$767.80		$819.8885	$819.89	$819.90	$819.80