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	$174.69	12.355%	$196.2729	$196.27	$196.25	$196.30
Purchase #2	$140.75	12.398%	$158.2002	$158.20	$158.20	$158.20
Purchase #3	$42.43	8.531%	$46.0497	$46.05	$46.05	$46.00
Purchase #4	$196.56	13.835%	$223.7541	$223.75	$223.75	$223.80
Purchase #5	$154.37	9.659%	$169.2806	$169.28	$169.30	$169.30
Purchase #6	$145.91	3.235%	$150.6302	$150.63	$150.65	$150.60
Purchase #7	$201.86	8.257%	$218.5276	$218.53	$218.55	$218.50
7 purchase totals =	$1,056.57		$1,162.7153	$1,162.71	$1,162.75	$1,162.70