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	$221.97	5.611%	$234.4247	$234.42	$234.40	$234.40
Purchase #2	$247.47	3.400%	$255.884	$255.88	$255.90	$255.90
Purchase #3	$244.62	7.292%	$262.4577	$262.46	$262.45	$262.50
Purchase #4	$179.39	4.118%	$186.7773	$186.78	$186.80	$186.80
Purchase #5	$88.70	13.113%	$100.3312	$100.33	$100.35	$100.30
Purchase #6	$84.99	4.823%	$89.0891	$89.09	$89.10	$89.10
Purchase #7	$199.83	7.814%	$215.4447	$215.44	$215.45	$215.40
7 purchase totals =	$1,266.97		$1,344.4087	$1,344.40	$1,344.45	$1,344.40