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	$246.25	10.123%	$271.1779	$271.18	$271.20	$271.20
Purchase #2	$132.65	7.142%	$142.1239	$142.12	$142.10	$142.10
Purchase #3	$166.64	3.512%	$172.4924	$172.49	$172.50	$172.50
Purchase #4	$167.82	11.142%	$186.5185	$186.52	$186.50	$186.50
Purchase #5	$151.92	11.666%	$169.643	$169.64	$169.65	$169.60
Purchase #6	$64.38	12.227%	$72.2517	$72.25	$72.25	$72.30
Purchase #7	$140.76	9.179%	$153.6804	$153.68	$153.70	$153.70
7 purchase totals =	$1,070.42		$1,167.8878	$1,167.88	$1,167.90	$1,167.90