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	$33.39	4.135%	$34.7707	$34.77	$34.75	$34.80
Purchase #2	$196.72	3.179%	$202.9737	$202.97	$202.95	$203.00
Purchase #3	$93.41	13.459%	$105.9821	$105.98	$106.00	$106.00
Purchase #4	$116.28	6.120%	$123.3963	$123.40	$123.40	$123.40
Purchase #5	$153.60	7.108%	$164.5179	$164.52	$164.50	$164.50
Purchase #6	$67.47	7.416%	$72.4736	$72.47	$72.45	$72.50
Purchase #7	$143.27	5.245%	$150.7845	$150.78	$150.80	$150.80
7 purchase totals =	$804.14		$854.8988	$854.89	$854.85	$855.00