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	$188.74	5.348%	$198.8338	$198.83	$198.85	$198.80
Purchase #2	$148.61	9.343%	$162.4946	$162.49	$162.50	$162.50
Purchase #3	$88.40	12.553%	$99.4969	$99.50	$99.50	$99.50
Purchase #4	$208.63	3.289%	$215.4918	$215.49	$215.50	$215.50
Purchase #5	$71.65	12.494%	$80.602	$80.60	$80.60	$80.60
Purchase #6	$225.96	9.276%	$246.92	$246.92	$246.90	$246.90
Purchase #7	$216.84	10.699%	$240.0397	$240.04	$240.05	$240.00
7 purchase totals =	$1,148.83		$1,243.8788	$1,243.87	$1,243.90	$1,243.80