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	$139.65	5.769%	$147.7064	$147.71	$147.70	$147.70
Purchase #2	$236.60	10.454%	$261.3342	$261.33	$261.35	$261.30
Purchase #3	$17.78	4.104%	$18.5097	$18.51	$18.50	$18.50
Purchase #4	$63.42	12.391%	$71.2784	$71.28	$71.30	$71.30
Purchase #5	$211.53	5.284%	$222.7072	$222.71	$222.70	$222.70
Purchase #6	$64.25	12.536%	$72.3044	$72.30	$72.30	$72.30
Purchase #7	$249.44	4.705%	$261.1762	$261.18	$261.20	$261.20
7 purchase totals =	$982.67		$1,055.0165	$1,055.02	$1,055.05	$1,055.00