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	$150.56	3.684%	$156.1066	$156.11	$156.10	$156.10
Purchase #2	$167.62	10.585%	$185.3626	$185.36	$185.35	$185.40
Purchase #3	$101.45	7.589%	$109.149	$109.15	$109.15	$109.10
Purchase #4	$73.72	10.498%	$81.4591	$81.46	$81.45	$81.50
Purchase #5	$246.98	5.157%	$259.7168	$259.72	$259.70	$259.70
Purchase #6	$231.27	3.479%	$239.3159	$239.32	$239.30	$239.30
Purchase #7	$59.98	12.638%	$67.5603	$67.56	$67.55	$67.60
7 purchase totals =	$1,031.58		$1,098.6703	$1,098.68	$1,098.60	$1,098.70