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	$105.42	7.716%	$113.5542	$113.55	$113.55	$113.60
Purchase #2	$95.50	8.859%	$103.9603	$103.96	$103.95	$104.00
Purchase #3	$52.69	12.200%	$59.1182	$59.12	$59.10	$59.10
Purchase #4	$231.43	8.498%	$251.0969	$251.10	$251.10	$251.10
Purchase #5	$91.96	4.583%	$96.1745	$96.17	$96.15	$96.20
Purchase #6	$216.61	12.217%	$243.0732	$243.07	$243.05	$243.10
Purchase #7	$209.35	9.531%	$229.3031	$229.30	$229.30	$229.30
7 purchase totals =	$1,002.96		$1,096.2804	$1,096.27	$1,096.20	$1,096.40