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	$198.60	6.409%	$211.3283	$211.33	$211.35	$211.30
Purchase #2	$187.95	6.789%	$200.7099	$200.71	$200.70	$200.70
Purchase #3	$97.60	8.760%	$106.1498	$106.15	$106.15	$106.10
Purchase #4	$102.84	3.674%	$106.6183	$106.62	$106.60	$106.60
Purchase #5	$158.95	8.563%	$172.5609	$172.56	$172.55	$172.60
Purchase #6	$103.69	5.538%	$109.4324	$109.43	$109.45	$109.40
Purchase #7	$63.84	5.848%	$67.5734	$67.57	$67.55	$67.60
7 purchase totals =	$913.47		$974.3730	$974.37	$974.35	$974.30