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	$42.53	13.873%	$48.4302	$48.43	$48.45	$48.40
Purchase #2	$53.43	3.771%	$55.4448	$55.44	$55.45	$55.40
Purchase #3	$121.79	6.214%	$129.358	$129.36	$129.35	$129.40
Purchase #4	$231.55	8.208%	$250.5556	$250.56	$250.55	$250.60
Purchase #5	$134.80	13.102%	$152.4615	$152.46	$152.45	$152.50
Purchase #6	$236.76	5.390%	$249.5214	$249.52	$249.50	$249.50
Purchase #7	$180.83	10.818%	$200.3922	$200.39	$200.40	$200.40
7 purchase totals =	$1,001.69		$1,086.1637	$1,086.16	$1,086.15	$1,086.20