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	$234.95	9.728%	$257.8059	$257.81	$257.80	$257.80
Purchase #2	$165.34	3.593%	$171.2807	$171.28	$171.30	$171.30
Purchase #3	$56.83	10.624%	$62.8676	$62.87	$62.85	$62.90
Purchase #4	$229.47	10.553%	$253.686	$253.69	$253.70	$253.70
Purchase #5	$179.56	6.299%	$190.8705	$190.87	$190.85	$190.90
Purchase #6	$122.85	6.649%	$131.0183	$131.02	$131.00	$131.00
Purchase #7	$186.52	6.373%	$198.4069	$198.41	$198.40	$198.40
7 purchase totals =	$1,175.52		$1,265.9359	$1,265.95	$1,265.90	$1,266.00