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	$148.72	12.662%	$167.5509	$167.55	$167.55	$167.60
Purchase #2	$27.46	10.232%	$30.2697	$30.27	$30.25	$30.30
Purchase #3	$80.55	5.601%	$85.0616	$85.06	$85.05	$85.10
Purchase #4	$50.25	10.453%	$55.5026	$55.50	$55.50	$55.50
Purchase #5	$150.78	13.493%	$171.1247	$171.12	$171.10	$171.10
Purchase #6	$50.53	8.215%	$54.681	$54.68	$54.70	$54.70
Purchase #7	$162.55	13.763%	$184.9218	$184.92	$184.90	$184.90
7 purchase totals =	$670.84		$749.1123	$749.10	$749.05	$749.20