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	$127.50	5.417%	$134.4067	$134.41	$134.40	$134.40
Purchase #2	$172.63	13.768%	$196.3977	$196.40	$196.40	$196.40
Purchase #3	$191.94	4.178%	$199.9593	$199.96	$199.95	$200.00
Purchase #4	$99.51	13.120%	$112.5657	$112.57	$112.55	$112.60
Purchase #5	$91.80	12.594%	$103.3613	$103.36	$103.35	$103.40
Purchase #6	$236.61	4.239%	$246.6399	$246.64	$246.65	$246.60
Purchase #7	$110.67	3.447%	$114.4848	$114.48	$114.50	$114.50
7 purchase totals =	$1,030.66		$1,107.8154	$1,107.82	$1,107.80	$1,107.90