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	$84.67	3.641%	$87.7528	$87.75	$87.75	$87.80
Purchase #2	$68.83	13.383%	$78.0415	$78.04	$78.05	$78.00
Purchase #3	$50.25	13.118%	$56.8418	$56.84	$56.85	$56.80
Purchase #4	$160.72	7.712%	$173.1147	$173.11	$173.10	$173.10
Purchase #5	$59.37	13.774%	$67.5476	$67.55	$67.55	$67.50
Purchase #6	$183.31	8.363%	$198.6402	$198.64	$198.65	$198.60
Purchase #7	$93.92	11.681%	$104.8908	$104.89	$104.90	$104.90
7 purchase totals =	$701.07		$766.8294	$766.82	$766.85	$766.70