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	$137.42	8.303%	$148.83	$148.83	$148.85	$148.80
Purchase #2	$222.45	9.285%	$243.1045	$243.10	$243.10	$243.10
Purchase #3	$193.42	11.635%	$215.9244	$215.92	$215.90	$215.90
Purchase #4	$167.68	11.229%	$186.5088	$186.51	$186.50	$186.50
Purchase #5	$234.56	11.749%	$262.1185	$262.12	$262.10	$262.10
Purchase #6	$174.31	6.598%	$185.811	$185.81	$185.80	$185.80
Purchase #7	$213.48	12.108%	$239.3282	$239.33	$239.35	$239.30
7 purchase totals =	$1,343.32		$1,481.6254	$1,481.62	$1,481.60	$1,481.50