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	$104.56	7.582%	$112.4877	$112.49	$112.50	$112.50
Purchase #2	$125.75	4.526%	$131.4414	$131.44	$131.45	$131.40
Purchase #3	$113.67	4.470%	$118.751	$118.75	$118.75	$118.80
Purchase #4	$60.60	5.567%	$63.9736	$63.97	$63.95	$64.00
Purchase #5	$185.85	5.722%	$196.4843	$196.48	$196.50	$196.50
Purchase #6	$177.98	10.641%	$196.9189	$196.92	$196.90	$196.90
Purchase #7	$238.88	12.631%	$269.0529	$269.05	$269.05	$269.10
7 purchase totals =	$1,007.29		$1,089.1098	$1,089.10	$1,089.10	$1,089.20