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	$98.41	13.351%	$111.5487	$111.55	$111.55	$111.50
Purchase #2	$119.33	3.829%	$123.8991	$123.90	$123.90	$123.90
Purchase #3	$204.31	5.649%	$215.8515	$215.85	$215.85	$215.90
Purchase #4	$229.36	3.142%	$236.5665	$236.57	$236.55	$236.60
Purchase #5	$104.39	13.422%	$118.4012	$118.40	$118.40	$118.40
Purchase #6	$234.39	4.540%	$245.0313	$245.03	$245.05	$245.00
Purchase #7	$95.86	7.424%	$102.9766	$102.98	$103.00	$103.00
7 purchase totals =	$1,086.05		$1,154.2749	$1,154.28	$1,154.30	$1,154.30