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	$82.79	7.626%	$89.1036	$89.10	$89.10	$89.10
Purchase #2	$113.52	4.561%	$118.6976	$118.70	$118.70	$118.70
Purchase #3	$70.58	4.355%	$73.6538	$73.65	$73.65	$73.70
Purchase #4	$180.88	12.522%	$203.5298	$203.53	$203.55	$203.50
Purchase #5	$97.42	6.573%	$103.8234	$103.82	$103.80	$103.80
Purchase #6	$136.60	6.348%	$145.2714	$145.27	$145.25	$145.30
Purchase #7	$67.52	6.661%	$72.0175	$72.02	$72.00	$72.00
7 purchase totals =	$749.31		$806.0971	$806.09	$806.05	$806.10