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	$145.44	3.657%	$150.7587	$150.76	$150.75	$150.80
Purchase #2	$82.88	3.855%	$86.075	$86.08	$86.10	$86.10
Purchase #3	$141.61	3.121%	$146.0296	$146.03	$146.05	$146.00
Purchase #4	$217.79	10.456%	$240.5621	$240.56	$240.55	$240.60
Purchase #5	$113.72	5.370%	$119.8268	$119.83	$119.85	$119.80
Purchase #6	$194.72	9.518%	$213.2534	$213.25	$213.25	$213.30
Purchase #7	$102.35	12.403%	$115.0445	$115.04	$115.05	$115.00
7 purchase totals =	$998.51		$1,071.5501	$1,071.55	$1,071.60	$1,071.60