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	$96.88	9.241%	$105.8327	$105.83	$105.85	$105.80
Purchase #2	$46.94	11.762%	$52.4611	$52.46	$52.45	$52.50
Purchase #3	$48.40	10.589%	$53.5251	$53.53	$53.55	$53.50
Purchase #4	$58.77	11.310%	$65.4169	$65.42	$65.40	$65.40
Purchase #5	$193.94	11.192%	$215.6458	$215.65	$215.65	$215.60
Purchase #6	$53.67	11.366%	$59.7701	$59.77	$59.75	$59.80
Purchase #7	$120.80	3.296%	$124.7816	$124.78	$124.80	$124.80
7 purchase totals =	$619.40		$677.4333	$677.44	$677.45	$677.40