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	$84.73	9.140%	$92.4743	$92.47	$92.45	$92.50
Purchase #2	$64.72	6.315%	$68.8071	$68.81	$68.80	$68.80
Purchase #3	$167.48	13.187%	$189.5656	$189.57	$189.55	$189.60
Purchase #4	$147.99	5.474%	$156.091	$156.09	$156.10	$156.10
Purchase #5	$154.43	11.202%	$171.7292	$171.73	$171.75	$171.70
Purchase #6	$213.91	4.280%	$223.0653	$223.07	$223.05	$223.10
Purchase #7	$174.95	12.334%	$196.5283	$196.53	$196.55	$196.50
7 purchase totals =	$1,008.21		$1,098.2608	$1,098.27	$1,098.25	$1,098.30