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	$172.53	13.739%	$196.2339	$196.23	$196.25	$196.20
Purchase #2	$185.68	7.746%	$200.0628	$200.06	$200.05	$200.10
Purchase #3	$127.51	8.542%	$138.4019	$138.40	$138.40	$138.40
Purchase #4	$97.81	13.177%	$110.6984	$110.70	$110.70	$110.70
Purchase #5	$166.44	11.481%	$185.549	$185.55	$185.55	$185.50
Purchase #6	$188.47	5.188%	$198.2478	$198.25	$198.25	$198.20
Purchase #7	$162.98	5.310%	$171.6342	$171.63	$171.65	$171.60
7 purchase totals =	$1,101.42		$1,200.8280	$1,200.82	$1,200.85	$1,200.70