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	$181.80	13.661%	$206.6357	$206.64	$206.65	$206.60
Purchase #2	$6.46	11.520%	$7.2042	$7.20	$7.20	$7.20
Purchase #3	$156.42	6.580%	$166.7124	$166.71	$166.70	$166.70
Purchase #4	$209.59	6.300%	$222.7942	$222.79	$222.80	$222.80
Purchase #5	$25.96	5.314%	$27.3395	$27.34	$27.35	$27.30
Purchase #6	$179.27	8.730%	$194.9203	$194.92	$194.90	$194.90
Purchase #7	$154.35	11.134%	$171.5353	$171.54	$171.55	$171.50
7 purchase totals =	$913.85		$997.1416	$997.14	$997.15	$997.00