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	$150.25	11.652%	$167.7571	$167.76	$167.75	$167.80
Purchase #2	$166.96	4.241%	$174.0408	$174.04	$174.05	$174.00
Purchase #3	$102.89	6.509%	$109.5871	$109.59	$109.60	$109.60
Purchase #4	$199.87	12.648%	$225.1496	$225.15	$225.15	$225.10
Purchase #5	$181.54	3.123%	$187.2095	$187.21	$187.20	$187.20
Purchase #6	$248.48	6.378%	$264.3281	$264.33	$264.35	$264.30
Purchase #7	$68.52	5.748%	$72.4585	$72.46	$72.45	$72.50
7 purchase totals =	$1,118.51		$1,200.5307	$1,200.54	$1,200.55	$1,200.50