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	$202.64	11.748%	$226.4461	$226.45	$226.45	$226.40
Purchase #2	$92.57	9.112%	$101.005	$101.01	$101.00	$101.00
Purchase #3	$56.56	10.455%	$62.4733	$62.47	$62.45	$62.50
Purchase #4	$183.34	10.134%	$201.9197	$201.92	$201.90	$201.90
Purchase #5	$67.48	7.213%	$72.3473	$72.35	$72.35	$72.30
Purchase #6	$160.65	12.353%	$180.4951	$180.50	$180.50	$180.50
Purchase #7	$141.77	13.479%	$160.8792	$160.88	$160.90	$160.90
7 purchase totals =	$905.01		$1,005.5657	$1,005.58	$1,005.55	$1,005.50