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	$235.77	8.473%	$255.7468	$255.75	$255.75	$255.70
Purchase #2	$59.58	4.384%	$62.192	$62.19	$62.20	$62.20
Purchase #3	$231.47	4.728%	$242.4139	$242.41	$242.40	$242.40
Purchase #4	$117.89	10.498%	$130.2661	$130.27	$130.25	$130.30
Purchase #5	$174.93	10.610%	$193.4901	$193.49	$193.50	$193.50
Purchase #6	$156.50	7.562%	$168.3345	$168.33	$168.35	$168.30
Purchase #7	$120.90	13.788%	$137.5697	$137.57	$137.55	$137.60
7 purchase totals =	$1,097.04		$1,190.0131	$1,190.01	$1,190.00	$1,190.00