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	$114.94	4.496%	$120.1077	$120.11	$120.10	$120.10
Purchase #2	$75.56	8.209%	$81.7627	$81.76	$81.75	$81.80
Purchase #3	$243.30	5.174%	$255.8883	$255.89	$255.90	$255.90
Purchase #4	$239.72	7.445%	$257.5672	$257.57	$257.55	$257.60
Purchase #5	$157.98	11.783%	$176.5948	$176.59	$176.60	$176.60
Purchase #6	$120.56	9.251%	$131.713	$131.71	$131.70	$131.70
Purchase #7	$106.33	3.333%	$109.874	$109.87	$109.85	$109.90
7 purchase totals =	$1,058.39		$1,133.5077	$1,133.50	$1,133.45	$1,133.60