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	$95.50	7.289%	$102.461	$102.46	$102.45	$102.50
Purchase #2	$85.81	10.835%	$95.1075	$95.11	$95.10	$95.10
Purchase #3	$164.61	12.730%	$185.5649	$185.56	$185.55	$185.60
Purchase #4	$131.48	12.782%	$148.2858	$148.29	$148.30	$148.30
Purchase #5	$74.49	4.714%	$78.0015	$78.00	$78.00	$78.00
Purchase #6	$209.72	4.390%	$218.9267	$218.93	$218.95	$218.90
Purchase #7	$24.49	12.206%	$27.4792	$27.48	$27.50	$27.50
7 purchase totals =	$786.10		$855.8266	$855.83	$855.85	$855.90