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	$87.98	9.606%	$96.4314	$96.43	$96.45	$96.40
Purchase #2	$156.74	5.731%	$165.7228	$165.72	$165.70	$165.70
Purchase #3	$203.27	13.412%	$230.5326	$230.53	$230.55	$230.50
Purchase #4	$184.60	5.420%	$194.6053	$194.61	$194.60	$194.60
Purchase #5	$63.43	12.566%	$71.4006	$71.40	$71.40	$71.40
Purchase #6	$241.29	3.809%	$250.4807	$250.48	$250.50	$250.50
Purchase #7	$89.67	13.781%	$102.0274	$102.03	$102.05	$102.00
7 purchase totals =	$1,026.98		$1,111.2008	$1,111.20	$1,111.25	$1,111.10