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	$36.98	12.757%	$41.6975	$41.70	$41.70	$41.70
Purchase #2	$71.58	6.281%	$76.0759	$76.08	$76.10	$76.10
Purchase #3	$148.69	12.706%	$167.5826	$167.58	$167.60	$167.60
Purchase #4	$211.71	12.691%	$238.5781	$238.58	$238.60	$238.60
Purchase #5	$198.66	12.157%	$222.8111	$222.81	$222.80	$222.80
Purchase #6	$181.59	12.814%	$204.8589	$204.86	$204.85	$204.90
Purchase #7	$219.94	11.240%	$244.6613	$244.66	$244.65	$244.70
7 purchase totals =	$1,069.15		$1,196.2654	$1,196.27	$1,196.30	$1,196.40