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	$160.47	13.223%	$181.6889	$181.69	$181.70	$181.70
Purchase #2	$97.36	5.106%	$102.3312	$102.33	$102.35	$102.30
Purchase #3	$105.58	3.804%	$109.5963	$109.60	$109.60	$109.60
Purchase #4	$198.80	8.310%	$215.3203	$215.32	$215.30	$215.30
Purchase #5	$209.90	8.869%	$228.516	$228.52	$228.50	$228.50
Purchase #6	$13.91	11.527%	$15.5134	$15.51	$15.50	$15.50
Purchase #7	$248.59	11.673%	$277.6079	$277.61	$277.60	$277.60
7 purchase totals =	$1,034.61		$1,130.5740	$1,130.58	$1,130.55	$1,130.50