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	$198.72	13.334%	$225.2173	$225.22	$225.20	$225.20
Purchase #2	$135.94	6.318%	$144.5287	$144.53	$144.55	$144.50
Purchase #3	$80.63	4.583%	$84.3253	$84.33	$84.35	$84.30
Purchase #4	$177.64	4.642%	$185.886	$185.89	$185.90	$185.90
Purchase #5	$179.49	5.286%	$188.9778	$188.98	$189.00	$189.00
Purchase #6	$202.44	10.385%	$223.4634	$223.46	$223.45	$223.50
Purchase #7	$92.63	8.428%	$100.4369	$100.44	$100.45	$100.40
7 purchase totals =	$1,067.49		$1,152.8354	$1,152.85	$1,152.90	$1,152.80