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	$218.89	11.360%	$243.7559	$243.76	$243.75	$243.80
Purchase #2	$33.57	5.762%	$35.5043	$35.50	$35.50	$35.50
Purchase #3	$35.81	13.629%	$40.6905	$40.69	$40.70	$40.70
Purchase #4	$181.87	5.177%	$191.2854	$191.29	$191.30	$191.30
Purchase #5	$143.36	7.830%	$154.5851	$154.59	$154.60	$154.60
Purchase #6	$194.42	10.562%	$214.9546	$214.95	$214.95	$215.00
Purchase #7	$37.40	10.656%	$41.3853	$41.39	$41.40	$41.40
7 purchase totals =	$845.32		$922.1611	$922.17	$922.20	$922.30