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	$162.40	7.634%	$174.7976	$174.80	$174.80	$174.80
Purchase #2	$56.63	10.108%	$62.3542	$62.35	$62.35	$62.40
Purchase #3	$84.62	5.264%	$89.0744	$89.07	$89.05	$89.10
Purchase #4	$36.57	12.656%	$41.1983	$41.20	$41.20	$41.20
Purchase #5	$62.78	4.638%	$65.6917	$65.69	$65.70	$65.70
Purchase #6	$173.46	7.182%	$185.9179	$185.92	$185.90	$185.90
Purchase #7	$61.63	9.327%	$67.3782	$67.38	$67.40	$67.40
7 purchase totals =	$638.09		$686.4123	$686.41	$686.40	$686.50