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	$113.81	4.367%	$118.7801	$118.78	$118.80	$118.80
Purchase #2	$146.76	6.560%	$156.3875	$156.39	$156.40	$156.40
Purchase #3	$218.41	10.333%	$240.9783	$240.98	$241.00	$241.00
Purchase #4	$168.61	7.240%	$180.8174	$180.82	$180.80	$180.80
Purchase #5	$97.65	5.724%	$103.2395	$103.24	$103.25	$103.20
Purchase #6	$130.40	6.517%	$138.8982	$138.90	$138.90	$138.90
Purchase #7	$245.59	6.363%	$261.2169	$261.22	$261.20	$261.20
7 purchase totals =	$1,121.23		$1,200.3179	$1,200.33	$1,200.35	$1,200.30