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	$159.43	4.522%	$166.6394	$166.64	$166.65	$166.60
Purchase #2	$85.94	4.486%	$89.7953	$89.80	$89.80	$89.80
Purchase #3	$102.29	10.364%	$112.8913	$112.89	$112.90	$112.90
Purchase #4	$153.58	3.736%	$159.3177	$159.32	$159.30	$159.30
Purchase #5	$215.25	12.642%	$242.4619	$242.46	$242.45	$242.50
Purchase #6	$195.38	13.214%	$221.1975	$221.20	$221.20	$221.20
Purchase #7	$60.26	5.486%	$63.5659	$63.57	$63.55	$63.60
7 purchase totals =	$972.13		$1,055.8690	$1,055.88	$1,055.85	$1,055.90