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	$54.83	3.577%	$56.7913	$56.79	$56.80	$56.80
Purchase #2	$217.98	5.298%	$229.5286	$229.53	$229.55	$229.50
Purchase #3	$215.72	4.517%	$225.4641	$225.46	$225.45	$225.50
Purchase #4	$95.91	4.745%	$100.4609	$100.46	$100.45	$100.50
Purchase #5	$84.88	6.181%	$90.1264	$90.13	$90.15	$90.10
Purchase #6	$193.71	8.237%	$209.6659	$209.67	$209.65	$209.70
Purchase #7	$111.86	3.141%	$115.3735	$115.37	$115.35	$115.40
7 purchase totals =	$974.89		$1,027.4107	$1,027.41	$1,027.40	$1,027.50