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	$118.32	11.397%	$131.8049	$131.80	$131.80	$131.80
Purchase #2	$210.36	6.311%	$223.6358	$223.64	$223.65	$223.60
Purchase #3	$211.83	11.738%	$236.6946	$236.69	$236.70	$236.70
Purchase #4	$41.32	13.421%	$46.8656	$46.87	$46.85	$46.90
Purchase #5	$232.56	10.409%	$256.7672	$256.77	$256.75	$256.80
Purchase #6	$194.64	4.748%	$203.8815	$203.88	$203.90	$203.90
Purchase #7	$58.29	10.853%	$64.6162	$64.62	$64.60	$64.60
7 purchase totals =	$1,067.32		$1,164.2658	$1,164.27	$1,164.25	$1,164.30