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	$151.35	10.308%	$166.9512	$166.95	$166.95	$167.00
Purchase #2	$97.51	5.841%	$103.2056	$103.21	$103.20	$103.20
Purchase #3	$26.43	4.312%	$27.5697	$27.57	$27.55	$27.60
Purchase #4	$115.45	10.501%	$127.5734	$127.57	$127.55	$127.60
Purchase #5	$164.56	13.228%	$186.328	$186.33	$186.35	$186.30
Purchase #6	$74.77	11.449%	$83.3304	$83.33	$83.35	$83.30
Purchase #7	$142.84	6.375%	$151.9461	$151.95	$151.95	$151.90
7 purchase totals =	$772.91		$846.9044	$846.91	$846.90	$846.90