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	$176.52	5.471%	$186.1774	$186.18	$186.20	$186.20
Purchase #2	$167.52	12.645%	$188.7029	$188.70	$188.70	$188.70
Purchase #3	$92.42	13.756%	$105.1333	$105.13	$105.15	$105.10
Purchase #4	$24.25	12.718%	$27.3341	$27.33	$27.35	$27.30
Purchase #5	$196.41	9.594%	$215.2536	$215.25	$215.25	$215.30
Purchase #6	$148.29	11.296%	$165.0408	$165.04	$165.05	$165.00
Purchase #7	$217.53	10.709%	$240.8253	$240.83	$240.85	$240.80
7 purchase totals =	$1,022.94		$1,128.4674	$1,128.46	$1,128.55	$1,128.40